1 2 /* pngread.c - read a PNG file 3 * 4 * Copyright (c) 2018-2019 Cosmin Truta 5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson 6 * Copyright (c) 1996-1997 Andreas Dilger 7 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. 8 * 9 * This code is released under the libpng license. 10 * For conditions of distribution and use, see the disclaimer 11 * and license in png.h 12 * 13 * This file contains routines that an application calls directly to 14 * read a PNG file or stream. 15 */ 16 17 #include "pngpriv.h" 18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED) 19 # include <errno.h> 20 #endif 21 22 #ifdef PNG_READ_SUPPORTED 23 24 /* Create a PNG structure for reading, and allocate any memory needed. */ 25 PNG_FUNCTION(png_structp,PNGAPI 26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr, 27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED) 28 { 29 #ifndef PNG_USER_MEM_SUPPORTED 30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr, 31 error_fn, warn_fn, NULL, NULL, NULL); 32 #else 33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn, 34 warn_fn, NULL, NULL, NULL); 35 } 36 37 /* Alternate create PNG structure for reading, and allocate any memory 38 * needed. 39 */ 40 PNG_FUNCTION(png_structp,PNGAPI 41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr, 42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr, 43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED) 44 { 45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr, 46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn); 47 #endif /* USER_MEM */ 48 49 if (png_ptr != NULL) 50 { 51 png_ptr->mode = PNG_IS_READ_STRUCT; 52 53 /* Added in libpng-1.6.0; this can be used to detect a read structure if 54 * required (it will be zero in a write structure.) 55 */ 56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED 57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE; 58 # endif 59 60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED 61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN; 62 63 /* In stable builds only warn if an application error can be completely 64 * handled. 65 */ 66 # if PNG_RELEASE_BUILD 67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN; 68 # endif 69 # endif 70 71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't 72 * do it itself) avoiding setting the default function if it is not 73 * required. 74 */ 75 png_set_read_fn(png_ptr, NULL, NULL); 76 } 77 78 return png_ptr; 79 } 80 81 82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 83 /* Read the information before the actual image data. This has been 84 * changed in v0.90 to allow reading a file that already has the magic 85 * bytes read from the stream. You can tell libpng how many bytes have 86 * been read from the beginning of the stream (up to the maximum of 8) 87 * via png_set_sig_bytes(), and we will only check the remaining bytes 88 * here. The application can then have access to the signature bytes we 89 * read if it is determined that this isn't a valid PNG file. 90 */ 91 void PNGAPI 92 png_read_info(png_structrp png_ptr, png_inforp info_ptr) 93 { 94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 95 int keep; 96 #endif 97 98 png_debug(1, "in png_read_info"); 99 100 if (png_ptr == NULL || info_ptr == NULL) 101 return; 102 103 /* Read and check the PNG file signature. */ 104 png_read_sig(png_ptr, info_ptr); 105 106 for (;;) 107 { 108 png_uint_32 length = png_read_chunk_header(png_ptr); 109 png_uint_32 chunk_name = png_ptr->chunk_name; 110 111 /* IDAT logic needs to happen here to simplify getting the two flags 112 * right. 113 */ 114 if (chunk_name == png_IDAT) 115 { 116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0) 117 png_chunk_error(png_ptr, "Missing IHDR before IDAT"); 118 119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE && 120 (png_ptr->mode & PNG_HAVE_PLTE) == 0) 121 png_chunk_error(png_ptr, "Missing PLTE before IDAT"); 122 123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0) 124 png_chunk_benign_error(png_ptr, "Too many IDATs found"); 125 126 png_ptr->mode |= PNG_HAVE_IDAT; 127 } 128 129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0) 130 { 131 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT; 132 png_ptr->mode |= PNG_AFTER_IDAT; 133 } 134 135 /* This should be a binary subdivision search or a hash for 136 * matching the chunk name rather than a linear search. 137 */ 138 if (chunk_name == png_IHDR) 139 png_handle_IHDR(png_ptr, info_ptr, length); 140 141 else if (chunk_name == png_IEND) 142 png_handle_IEND(png_ptr, info_ptr, length); 143 144 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 145 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0) 146 { 147 png_handle_unknown(png_ptr, info_ptr, length, keep); 148 149 if (chunk_name == png_PLTE) 150 png_ptr->mode |= PNG_HAVE_PLTE; 151 152 else if (chunk_name == png_IDAT) 153 { 154 png_ptr->idat_size = 0; /* It has been consumed */ 155 break; 156 } 157 } 158 #endif 159 else if (chunk_name == png_PLTE) 160 png_handle_PLTE(png_ptr, info_ptr, length); 161 162 else if (chunk_name == png_IDAT) 163 { 164 png_ptr->idat_size = length; 165 break; 166 } 167 168 #ifdef PNG_READ_bKGD_SUPPORTED 169 else if (chunk_name == png_bKGD) 170 png_handle_bKGD(png_ptr, info_ptr, length); 171 #endif 172 173 #ifdef PNG_READ_cHRM_SUPPORTED 174 else if (chunk_name == png_cHRM) 175 png_handle_cHRM(png_ptr, info_ptr, length); 176 #endif 177 178 #ifdef PNG_READ_eXIf_SUPPORTED 179 else if (chunk_name == png_eXIf) 180 png_handle_eXIf(png_ptr, info_ptr, length); 181 #endif 182 183 #ifdef PNG_READ_gAMA_SUPPORTED 184 else if (chunk_name == png_gAMA) 185 png_handle_gAMA(png_ptr, info_ptr, length); 186 #endif 187 188 #ifdef PNG_READ_hIST_SUPPORTED 189 else if (chunk_name == png_hIST) 190 png_handle_hIST(png_ptr, info_ptr, length); 191 #endif 192 193 #ifdef PNG_READ_oFFs_SUPPORTED 194 else if (chunk_name == png_oFFs) 195 png_handle_oFFs(png_ptr, info_ptr, length); 196 #endif 197 198 #ifdef PNG_READ_pCAL_SUPPORTED 199 else if (chunk_name == png_pCAL) 200 png_handle_pCAL(png_ptr, info_ptr, length); 201 #endif 202 203 #ifdef PNG_READ_sCAL_SUPPORTED 204 else if (chunk_name == png_sCAL) 205 png_handle_sCAL(png_ptr, info_ptr, length); 206 #endif 207 208 #ifdef PNG_READ_pHYs_SUPPORTED 209 else if (chunk_name == png_pHYs) 210 png_handle_pHYs(png_ptr, info_ptr, length); 211 #endif 212 213 #ifdef PNG_READ_sBIT_SUPPORTED 214 else if (chunk_name == png_sBIT) 215 png_handle_sBIT(png_ptr, info_ptr, length); 216 #endif 217 218 #ifdef PNG_READ_sRGB_SUPPORTED 219 else if (chunk_name == png_sRGB) 220 png_handle_sRGB(png_ptr, info_ptr, length); 221 #endif 222 223 #ifdef PNG_READ_iCCP_SUPPORTED 224 else if (chunk_name == png_iCCP) 225 png_handle_iCCP(png_ptr, info_ptr, length); 226 #endif 227 228 #ifdef PNG_READ_sPLT_SUPPORTED 229 else if (chunk_name == png_sPLT) 230 png_handle_sPLT(png_ptr, info_ptr, length); 231 #endif 232 233 #ifdef PNG_READ_tEXt_SUPPORTED 234 else if (chunk_name == png_tEXt) 235 png_handle_tEXt(png_ptr, info_ptr, length); 236 #endif 237 238 #ifdef PNG_READ_tIME_SUPPORTED 239 else if (chunk_name == png_tIME) 240 png_handle_tIME(png_ptr, info_ptr, length); 241 #endif 242 243 #ifdef PNG_READ_tRNS_SUPPORTED 244 else if (chunk_name == png_tRNS) 245 png_handle_tRNS(png_ptr, info_ptr, length); 246 #endif 247 248 #ifdef PNG_READ_zTXt_SUPPORTED 249 else if (chunk_name == png_zTXt) 250 png_handle_zTXt(png_ptr, info_ptr, length); 251 #endif 252 253 #ifdef PNG_READ_iTXt_SUPPORTED 254 else if (chunk_name == png_iTXt) 255 png_handle_iTXt(png_ptr, info_ptr, length); 256 #endif 257 258 else 259 png_handle_unknown(png_ptr, info_ptr, length, 260 PNG_HANDLE_CHUNK_AS_DEFAULT); 261 } 262 } 263 #endif /* SEQUENTIAL_READ */ 264 265 /* Optional call to update the users info_ptr structure */ 266 void PNGAPI 267 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr) 268 { 269 png_debug(1, "in png_read_update_info"); 270 271 if (png_ptr != NULL) 272 { 273 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 274 { 275 png_read_start_row(png_ptr); 276 277 # ifdef PNG_READ_TRANSFORMS_SUPPORTED 278 png_read_transform_info(png_ptr, info_ptr); 279 # else 280 PNG_UNUSED(info_ptr) 281 # endif 282 } 283 284 /* New in 1.6.0 this avoids the bug of doing the initializations twice */ 285 else 286 png_app_error(png_ptr, 287 "png_read_update_info/png_start_read_image: duplicate call"); 288 } 289 } 290 291 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 292 /* Initialize palette, background, etc, after transformations 293 * are set, but before any reading takes place. This allows 294 * the user to obtain a gamma-corrected palette, for example. 295 * If the user doesn't call this, we will do it ourselves. 296 */ 297 void PNGAPI 298 png_start_read_image(png_structrp png_ptr) 299 { 300 png_debug(1, "in png_start_read_image"); 301 302 if (png_ptr != NULL) 303 { 304 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 305 png_read_start_row(png_ptr); 306 307 /* New in 1.6.0 this avoids the bug of doing the initializations twice */ 308 else 309 png_app_error(png_ptr, 310 "png_start_read_image/png_read_update_info: duplicate call"); 311 } 312 } 313 #endif /* SEQUENTIAL_READ */ 314 315 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 316 #ifdef PNG_MNG_FEATURES_SUPPORTED 317 /* Undoes intrapixel differencing, 318 * NOTE: this is apparently only supported in the 'sequential' reader. 319 */ 320 static void 321 png_do_read_intrapixel(png_row_infop row_info, png_bytep row) 322 { 323 png_debug(1, "in png_do_read_intrapixel"); 324 325 if ( 326 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0) 327 { 328 int bytes_per_pixel; 329 png_uint_32 row_width = row_info->width; 330 331 if (row_info->bit_depth == 8) 332 { 333 png_bytep rp; 334 png_uint_32 i; 335 336 if (row_info->color_type == PNG_COLOR_TYPE_RGB) 337 bytes_per_pixel = 3; 338 339 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA) 340 bytes_per_pixel = 4; 341 342 else 343 return; 344 345 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel) 346 { 347 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff); 348 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff); 349 } 350 } 351 else if (row_info->bit_depth == 16) 352 { 353 png_bytep rp; 354 png_uint_32 i; 355 356 if (row_info->color_type == PNG_COLOR_TYPE_RGB) 357 bytes_per_pixel = 6; 358 359 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA) 360 bytes_per_pixel = 8; 361 362 else 363 return; 364 365 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel) 366 { 367 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1); 368 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3); 369 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5); 370 png_uint_32 red = (s0 + s1 + 65536) & 0xffff; 371 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff; 372 *(rp ) = (png_byte)((red >> 8) & 0xff); 373 *(rp + 1) = (png_byte)(red & 0xff); 374 *(rp + 4) = (png_byte)((blue >> 8) & 0xff); 375 *(rp + 5) = (png_byte)(blue & 0xff); 376 } 377 } 378 } 379 } 380 #endif /* MNG_FEATURES */ 381 382 void PNGAPI 383 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row) 384 { 385 png_row_info row_info; 386 387 if (png_ptr == NULL) 388 return; 389 390 png_debug2(1, "in png_read_row (row %lu, pass %d)", 391 (unsigned long)png_ptr->row_number, png_ptr->pass); 392 393 /* png_read_start_row sets the information (in particular iwidth) for this 394 * interlace pass. 395 */ 396 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 397 png_read_start_row(png_ptr); 398 399 /* 1.5.6: row_info moved out of png_struct to a local here. */ 400 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */ 401 row_info.color_type = png_ptr->color_type; 402 row_info.bit_depth = png_ptr->bit_depth; 403 row_info.channels = png_ptr->channels; 404 row_info.pixel_depth = png_ptr->pixel_depth; 405 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width); 406 407 #ifdef PNG_WARNINGS_SUPPORTED 408 if (png_ptr->row_number == 0 && png_ptr->pass == 0) 409 { 410 /* Check for transforms that have been set but were defined out */ 411 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED) 412 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0) 413 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined"); 414 #endif 415 416 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED) 417 if ((png_ptr->transformations & PNG_FILLER) != 0) 418 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined"); 419 #endif 420 421 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \ 422 !defined(PNG_READ_PACKSWAP_SUPPORTED) 423 if ((png_ptr->transformations & PNG_PACKSWAP) != 0) 424 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined"); 425 #endif 426 427 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED) 428 if ((png_ptr->transformations & PNG_PACK) != 0) 429 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined"); 430 #endif 431 432 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) 433 if ((png_ptr->transformations & PNG_SHIFT) != 0) 434 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined"); 435 #endif 436 437 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED) 438 if ((png_ptr->transformations & PNG_BGR) != 0) 439 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined"); 440 #endif 441 442 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED) 443 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0) 444 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined"); 445 #endif 446 } 447 #endif /* WARNINGS */ 448 449 #ifdef PNG_READ_INTERLACING_SUPPORTED 450 /* If interlaced and we do not need a new row, combine row and return. 451 * Notice that the pixels we have from previous rows have been transformed 452 * already; we can only combine like with like (transformed or 453 * untransformed) and, because of the libpng API for interlaced images, this 454 * means we must transform before de-interlacing. 455 */ 456 if (png_ptr->interlaced != 0 && 457 (png_ptr->transformations & PNG_INTERLACE) != 0) 458 { 459 switch (png_ptr->pass) 460 { 461 case 0: 462 if (png_ptr->row_number & 0x07) 463 { 464 if (dsp_row != NULL) 465 png_combine_row(png_ptr, dsp_row, 1/*display*/); 466 png_read_finish_row(png_ptr); 467 return; 468 } 469 break; 470 471 case 1: 472 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5) 473 { 474 if (dsp_row != NULL) 475 png_combine_row(png_ptr, dsp_row, 1/*display*/); 476 477 png_read_finish_row(png_ptr); 478 return; 479 } 480 break; 481 482 case 2: 483 if ((png_ptr->row_number & 0x07) != 4) 484 { 485 if (dsp_row != NULL && (png_ptr->row_number & 4)) 486 png_combine_row(png_ptr, dsp_row, 1/*display*/); 487 488 png_read_finish_row(png_ptr); 489 return; 490 } 491 break; 492 493 case 3: 494 if ((png_ptr->row_number & 3) || png_ptr->width < 3) 495 { 496 if (dsp_row != NULL) 497 png_combine_row(png_ptr, dsp_row, 1/*display*/); 498 499 png_read_finish_row(png_ptr); 500 return; 501 } 502 break; 503 504 case 4: 505 if ((png_ptr->row_number & 3) != 2) 506 { 507 if (dsp_row != NULL && (png_ptr->row_number & 2)) 508 png_combine_row(png_ptr, dsp_row, 1/*display*/); 509 510 png_read_finish_row(png_ptr); 511 return; 512 } 513 break; 514 515 case 5: 516 if ((png_ptr->row_number & 1) || png_ptr->width < 2) 517 { 518 if (dsp_row != NULL) 519 png_combine_row(png_ptr, dsp_row, 1/*display*/); 520 521 png_read_finish_row(png_ptr); 522 return; 523 } 524 break; 525 526 default: 527 case 6: 528 if ((png_ptr->row_number & 1) == 0) 529 { 530 png_read_finish_row(png_ptr); 531 return; 532 } 533 break; 534 } 535 } 536 #endif 537 538 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0) 539 png_error(png_ptr, "Invalid attempt to read row data"); 540 541 /* Fill the row with IDAT data: */ 542 png_ptr->row_buf[0]=255; /* to force error if no data was found */ 543 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1); 544 545 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE) 546 { 547 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST) 548 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1, 549 png_ptr->prev_row + 1, png_ptr->row_buf[0]); 550 else 551 png_error(png_ptr, "bad adaptive filter value"); 552 } 553 554 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before 555 * 1.5.6, while the buffer really is this big in current versions of libpng 556 * it may not be in the future, so this was changed just to copy the 557 * interlaced count: 558 */ 559 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1); 560 561 #ifdef PNG_MNG_FEATURES_SUPPORTED 562 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 && 563 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING)) 564 { 565 /* Intrapixel differencing */ 566 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1); 567 } 568 #endif 569 570 #ifdef PNG_READ_TRANSFORMS_SUPPORTED 571 if (png_ptr->transformations) 572 png_do_read_transformations(png_ptr, &row_info); 573 #endif 574 575 /* The transformed pixel depth should match the depth now in row_info. */ 576 if (png_ptr->transformed_pixel_depth == 0) 577 { 578 png_ptr->transformed_pixel_depth = row_info.pixel_depth; 579 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth) 580 png_error(png_ptr, "sequential row overflow"); 581 } 582 583 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth) 584 png_error(png_ptr, "internal sequential row size calculation error"); 585 586 #ifdef PNG_READ_INTERLACING_SUPPORTED 587 /* Expand interlaced rows to full size */ 588 if (png_ptr->interlaced != 0 && 589 (png_ptr->transformations & PNG_INTERLACE) != 0) 590 { 591 if (png_ptr->pass < 6) 592 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass, 593 png_ptr->transformations); 594 595 if (dsp_row != NULL) 596 png_combine_row(png_ptr, dsp_row, 1/*display*/); 597 598 if (row != NULL) 599 png_combine_row(png_ptr, row, 0/*row*/); 600 } 601 602 else 603 #endif 604 { 605 if (row != NULL) 606 png_combine_row(png_ptr, row, -1/*ignored*/); 607 608 if (dsp_row != NULL) 609 png_combine_row(png_ptr, dsp_row, -1/*ignored*/); 610 } 611 png_read_finish_row(png_ptr); 612 613 if (png_ptr->read_row_fn != NULL) 614 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass); 615 616 } 617 #endif /* SEQUENTIAL_READ */ 618 619 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 620 /* Read one or more rows of image data. If the image is interlaced, 621 * and png_set_interlace_handling() has been called, the rows need to 622 * contain the contents of the rows from the previous pass. If the 623 * image has alpha or transparency, and png_handle_alpha()[*] has been 624 * called, the rows contents must be initialized to the contents of the 625 * screen. 626 * 627 * "row" holds the actual image, and pixels are placed in it 628 * as they arrive. If the image is displayed after each pass, it will 629 * appear to "sparkle" in. "display_row" can be used to display a 630 * "chunky" progressive image, with finer detail added as it becomes 631 * available. If you do not want this "chunky" display, you may pass 632 * NULL for display_row. If you do not want the sparkle display, and 633 * you have not called png_handle_alpha(), you may pass NULL for rows. 634 * If you have called png_handle_alpha(), and the image has either an 635 * alpha channel or a transparency chunk, you must provide a buffer for 636 * rows. In this case, you do not have to provide a display_row buffer 637 * also, but you may. If the image is not interlaced, or if you have 638 * not called png_set_interlace_handling(), the display_row buffer will 639 * be ignored, so pass NULL to it. 640 * 641 * [*] png_handle_alpha() does not exist yet, as of this version of libpng 642 */ 643 644 void PNGAPI 645 png_read_rows(png_structrp png_ptr, png_bytepp row, 646 png_bytepp display_row, png_uint_32 num_rows) 647 { 648 png_uint_32 i; 649 png_bytepp rp; 650 png_bytepp dp; 651 652 png_debug(1, "in png_read_rows"); 653 654 if (png_ptr == NULL) 655 return; 656 657 rp = row; 658 dp = display_row; 659 if (rp != NULL && dp != NULL) 660 for (i = 0; i < num_rows; i++) 661 { 662 png_bytep rptr = *rp++; 663 png_bytep dptr = *dp++; 664 665 png_read_row(png_ptr, rptr, dptr); 666 } 667 668 else if (rp != NULL) 669 for (i = 0; i < num_rows; i++) 670 { 671 png_bytep rptr = *rp; 672 png_read_row(png_ptr, rptr, NULL); 673 rp++; 674 } 675 676 else if (dp != NULL) 677 for (i = 0; i < num_rows; i++) 678 { 679 png_bytep dptr = *dp; 680 png_read_row(png_ptr, NULL, dptr); 681 dp++; 682 } 683 } 684 #endif /* SEQUENTIAL_READ */ 685 686 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 687 /* Read the entire image. If the image has an alpha channel or a tRNS 688 * chunk, and you have called png_handle_alpha()[*], you will need to 689 * initialize the image to the current image that PNG will be overlaying. 690 * We set the num_rows again here, in case it was incorrectly set in 691 * png_read_start_row() by a call to png_read_update_info() or 692 * png_start_read_image() if png_set_interlace_handling() wasn't called 693 * prior to either of these functions like it should have been. You can 694 * only call this function once. If you desire to have an image for 695 * each pass of a interlaced image, use png_read_rows() instead. 696 * 697 * [*] png_handle_alpha() does not exist yet, as of this version of libpng 698 */ 699 void PNGAPI 700 png_read_image(png_structrp png_ptr, png_bytepp image) 701 { 702 png_uint_32 i, image_height; 703 int pass, j; 704 png_bytepp rp; 705 706 png_debug(1, "in png_read_image"); 707 708 if (png_ptr == NULL) 709 return; 710 711 #ifdef PNG_READ_INTERLACING_SUPPORTED 712 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 713 { 714 pass = png_set_interlace_handling(png_ptr); 715 /* And make sure transforms are initialized. */ 716 png_start_read_image(png_ptr); 717 } 718 else 719 { 720 if (png_ptr->interlaced != 0 && 721 (png_ptr->transformations & PNG_INTERLACE) == 0) 722 { 723 /* Caller called png_start_read_image or png_read_update_info without 724 * first turning on the PNG_INTERLACE transform. We can fix this here, 725 * but the caller should do it! 726 */ 727 png_warning(png_ptr, "Interlace handling should be turned on when " 728 "using png_read_image"); 729 /* Make sure this is set correctly */ 730 png_ptr->num_rows = png_ptr->height; 731 } 732 733 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in 734 * the above error case. 735 */ 736 pass = png_set_interlace_handling(png_ptr); 737 } 738 #else 739 if (png_ptr->interlaced) 740 png_error(png_ptr, 741 "Cannot read interlaced image -- interlace handler disabled"); 742 743 pass = 1; 744 #endif 745 746 image_height=png_ptr->height; 747 748 for (j = 0; j < pass; j++) 749 { 750 rp = image; 751 for (i = 0; i < image_height; i++) 752 { 753 png_read_row(png_ptr, *rp, NULL); 754 rp++; 755 } 756 } 757 } 758 #endif /* SEQUENTIAL_READ */ 759 760 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 761 /* Read the end of the PNG file. Will not read past the end of the 762 * file, will verify the end is accurate, and will read any comments 763 * or time information at the end of the file, if info is not NULL. 764 */ 765 void PNGAPI 766 png_read_end(png_structrp png_ptr, png_inforp info_ptr) 767 { 768 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 769 int keep; 770 #endif 771 772 png_debug(1, "in png_read_end"); 773 774 if (png_ptr == NULL) 775 return; 776 777 /* If png_read_end is called in the middle of reading the rows there may 778 * still be pending IDAT data and an owned zstream. Deal with this here. 779 */ 780 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 781 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0) 782 #endif 783 png_read_finish_IDAT(png_ptr); 784 785 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED 786 /* Report invalid palette index; added at libng-1.5.10 */ 787 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE && 788 png_ptr->num_palette_max > png_ptr->num_palette) 789 png_benign_error(png_ptr, "Read palette index exceeding num_palette"); 790 #endif 791 792 do 793 { 794 png_uint_32 length = png_read_chunk_header(png_ptr); 795 png_uint_32 chunk_name = png_ptr->chunk_name; 796 797 if (chunk_name != png_IDAT) 798 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT; 799 800 if (chunk_name == png_IEND) 801 png_handle_IEND(png_ptr, info_ptr, length); 802 803 else if (chunk_name == png_IHDR) 804 png_handle_IHDR(png_ptr, info_ptr, length); 805 806 else if (info_ptr == NULL) 807 png_crc_finish(png_ptr, length); 808 809 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 810 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0) 811 { 812 if (chunk_name == png_IDAT) 813 { 814 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED)) 815 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0) 816 png_benign_error(png_ptr, ".Too many IDATs found"); 817 } 818 png_handle_unknown(png_ptr, info_ptr, length, keep); 819 if (chunk_name == png_PLTE) 820 png_ptr->mode |= PNG_HAVE_PLTE; 821 } 822 #endif 823 824 else if (chunk_name == png_IDAT) 825 { 826 /* Zero length IDATs are legal after the last IDAT has been 827 * read, but not after other chunks have been read. 1.6 does not 828 * always read all the deflate data; specifically it cannot be relied 829 * upon to read the Adler32 at the end. If it doesn't ignore IDAT 830 * chunks which are longer than zero as well: 831 */ 832 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED)) 833 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0) 834 png_benign_error(png_ptr, "..Too many IDATs found"); 835 836 png_crc_finish(png_ptr, length); 837 } 838 else if (chunk_name == png_PLTE) 839 png_handle_PLTE(png_ptr, info_ptr, length); 840 841 #ifdef PNG_READ_bKGD_SUPPORTED 842 else if (chunk_name == png_bKGD) 843 png_handle_bKGD(png_ptr, info_ptr, length); 844 #endif 845 846 #ifdef PNG_READ_cHRM_SUPPORTED 847 else if (chunk_name == png_cHRM) 848 png_handle_cHRM(png_ptr, info_ptr, length); 849 #endif 850 851 #ifdef PNG_READ_eXIf_SUPPORTED 852 else if (chunk_name == png_eXIf) 853 png_handle_eXIf(png_ptr, info_ptr, length); 854 #endif 855 856 #ifdef PNG_READ_gAMA_SUPPORTED 857 else if (chunk_name == png_gAMA) 858 png_handle_gAMA(png_ptr, info_ptr, length); 859 #endif 860 861 #ifdef PNG_READ_hIST_SUPPORTED 862 else if (chunk_name == png_hIST) 863 png_handle_hIST(png_ptr, info_ptr, length); 864 #endif 865 866 #ifdef PNG_READ_oFFs_SUPPORTED 867 else if (chunk_name == png_oFFs) 868 png_handle_oFFs(png_ptr, info_ptr, length); 869 #endif 870 871 #ifdef PNG_READ_pCAL_SUPPORTED 872 else if (chunk_name == png_pCAL) 873 png_handle_pCAL(png_ptr, info_ptr, length); 874 #endif 875 876 #ifdef PNG_READ_sCAL_SUPPORTED 877 else if (chunk_name == png_sCAL) 878 png_handle_sCAL(png_ptr, info_ptr, length); 879 #endif 880 881 #ifdef PNG_READ_pHYs_SUPPORTED 882 else if (chunk_name == png_pHYs) 883 png_handle_pHYs(png_ptr, info_ptr, length); 884 #endif 885 886 #ifdef PNG_READ_sBIT_SUPPORTED 887 else if (chunk_name == png_sBIT) 888 png_handle_sBIT(png_ptr, info_ptr, length); 889 #endif 890 891 #ifdef PNG_READ_sRGB_SUPPORTED 892 else if (chunk_name == png_sRGB) 893 png_handle_sRGB(png_ptr, info_ptr, length); 894 #endif 895 896 #ifdef PNG_READ_iCCP_SUPPORTED 897 else if (chunk_name == png_iCCP) 898 png_handle_iCCP(png_ptr, info_ptr, length); 899 #endif 900 901 #ifdef PNG_READ_sPLT_SUPPORTED 902 else if (chunk_name == png_sPLT) 903 png_handle_sPLT(png_ptr, info_ptr, length); 904 #endif 905 906 #ifdef PNG_READ_tEXt_SUPPORTED 907 else if (chunk_name == png_tEXt) 908 png_handle_tEXt(png_ptr, info_ptr, length); 909 #endif 910 911 #ifdef PNG_READ_tIME_SUPPORTED 912 else if (chunk_name == png_tIME) 913 png_handle_tIME(png_ptr, info_ptr, length); 914 #endif 915 916 #ifdef PNG_READ_tRNS_SUPPORTED 917 else if (chunk_name == png_tRNS) 918 png_handle_tRNS(png_ptr, info_ptr, length); 919 #endif 920 921 #ifdef PNG_READ_zTXt_SUPPORTED 922 else if (chunk_name == png_zTXt) 923 png_handle_zTXt(png_ptr, info_ptr, length); 924 #endif 925 926 #ifdef PNG_READ_iTXt_SUPPORTED 927 else if (chunk_name == png_iTXt) 928 png_handle_iTXt(png_ptr, info_ptr, length); 929 #endif 930 931 else 932 png_handle_unknown(png_ptr, info_ptr, length, 933 PNG_HANDLE_CHUNK_AS_DEFAULT); 934 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0); 935 } 936 #endif /* SEQUENTIAL_READ */ 937 938 /* Free all memory used in the read struct */ 939 static void 940 png_read_destroy(png_structrp png_ptr) 941 { 942 png_debug(1, "in png_read_destroy"); 943 944 #ifdef PNG_READ_GAMMA_SUPPORTED 945 png_destroy_gamma_table(png_ptr); 946 #endif 947 948 png_free(png_ptr, png_ptr->big_row_buf); 949 png_ptr->big_row_buf = NULL; 950 png_free(png_ptr, png_ptr->big_prev_row); 951 png_ptr->big_prev_row = NULL; 952 png_free(png_ptr, png_ptr->read_buffer); 953 png_ptr->read_buffer = NULL; 954 955 #ifdef PNG_READ_QUANTIZE_SUPPORTED 956 png_free(png_ptr, png_ptr->palette_lookup); 957 png_ptr->palette_lookup = NULL; 958 png_free(png_ptr, png_ptr->quantize_index); 959 png_ptr->quantize_index = NULL; 960 #endif 961 962 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0) 963 { 964 png_zfree(png_ptr, png_ptr->palette); 965 png_ptr->palette = NULL; 966 } 967 png_ptr->free_me &= ~PNG_FREE_PLTE; 968 969 #if defined(PNG_tRNS_SUPPORTED) || \ 970 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) 971 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0) 972 { 973 png_free(png_ptr, png_ptr->trans_alpha); 974 png_ptr->trans_alpha = NULL; 975 } 976 png_ptr->free_me &= ~PNG_FREE_TRNS; 977 #endif 978 979 inflateEnd(&png_ptr->zstream); 980 981 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED 982 png_free(png_ptr, png_ptr->save_buffer); 983 png_ptr->save_buffer = NULL; 984 #endif 985 986 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \ 987 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) 988 png_free(png_ptr, png_ptr->unknown_chunk.data); 989 png_ptr->unknown_chunk.data = NULL; 990 #endif 991 992 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED 993 png_free(png_ptr, png_ptr->chunk_list); 994 png_ptr->chunk_list = NULL; 995 #endif 996 997 #if defined(PNG_READ_EXPAND_SUPPORTED) && \ 998 defined(PNG_ARM_NEON_IMPLEMENTATION) 999 png_free(png_ptr, png_ptr->riffled_palette); 1000 png_ptr->riffled_palette = NULL; 1001 #endif 1002 1003 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error 1004 * callbacks are still set at this point. They are required to complete the 1005 * destruction of the png_struct itself. 1006 */ 1007 } 1008 1009 /* Free all memory used by the read */ 1010 void PNGAPI 1011 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr, 1012 png_infopp end_info_ptr_ptr) 1013 { 1014 png_structrp png_ptr = NULL; 1015 1016 png_debug(1, "in png_destroy_read_struct"); 1017 1018 if (png_ptr_ptr != NULL) 1019 png_ptr = *png_ptr_ptr; 1020 1021 if (png_ptr == NULL) 1022 return; 1023 1024 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent 1025 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API. 1026 * The extra was, apparently, unnecessary yet this hides memory leak bugs. 1027 */ 1028 png_destroy_info_struct(png_ptr, end_info_ptr_ptr); 1029 png_destroy_info_struct(png_ptr, info_ptr_ptr); 1030 1031 *png_ptr_ptr = NULL; 1032 png_read_destroy(png_ptr); 1033 png_destroy_png_struct(png_ptr); 1034 } 1035 1036 void PNGAPI 1037 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn) 1038 { 1039 if (png_ptr == NULL) 1040 return; 1041 1042 png_ptr->read_row_fn = read_row_fn; 1043 } 1044 1045 1046 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 1047 #ifdef PNG_INFO_IMAGE_SUPPORTED 1048 void PNGAPI 1049 png_read_png(png_structrp png_ptr, png_inforp info_ptr, 1050 int transforms, voidp params) 1051 { 1052 if (png_ptr == NULL || info_ptr == NULL) 1053 return; 1054 1055 /* png_read_info() gives us all of the information from the 1056 * PNG file before the first IDAT (image data chunk). 1057 */ 1058 png_read_info(png_ptr, info_ptr); 1059 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep))) 1060 png_error(png_ptr, "Image is too high to process with png_read_png()"); 1061 1062 /* -------------- image transformations start here ------------------- */ 1063 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM 1064 * is not implemented. This will only happen in de-configured (non-default) 1065 * libpng builds. The results can be unexpected - png_read_png may return 1066 * short or mal-formed rows because the transform is skipped. 1067 */ 1068 1069 /* Tell libpng to strip 16-bit/color files down to 8 bits per color. 1070 */ 1071 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0) 1072 /* Added at libpng-1.5.4. "strip_16" produces the same result that it 1073 * did in earlier versions, while "scale_16" is now more accurate. 1074 */ 1075 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED 1076 png_set_scale_16(png_ptr); 1077 #else 1078 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported"); 1079 #endif 1080 1081 /* If both SCALE and STRIP are required pngrtran will effectively cancel the 1082 * latter by doing SCALE first. This is ok and allows apps not to check for 1083 * which is supported to get the right answer. 1084 */ 1085 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0) 1086 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED 1087 png_set_strip_16(png_ptr); 1088 #else 1089 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported"); 1090 #endif 1091 1092 /* Strip alpha bytes from the input data without combining with 1093 * the background (not recommended). 1094 */ 1095 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0) 1096 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED 1097 png_set_strip_alpha(png_ptr); 1098 #else 1099 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported"); 1100 #endif 1101 1102 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single 1103 * byte into separate bytes (useful for paletted and grayscale images). 1104 */ 1105 if ((transforms & PNG_TRANSFORM_PACKING) != 0) 1106 #ifdef PNG_READ_PACK_SUPPORTED 1107 png_set_packing(png_ptr); 1108 #else 1109 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported"); 1110 #endif 1111 1112 /* Change the order of packed pixels to least significant bit first 1113 * (not useful if you are using png_set_packing). 1114 */ 1115 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0) 1116 #ifdef PNG_READ_PACKSWAP_SUPPORTED 1117 png_set_packswap(png_ptr); 1118 #else 1119 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported"); 1120 #endif 1121 1122 /* Expand paletted colors into true RGB triplets 1123 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel 1124 * Expand paletted or RGB images with transparency to full alpha 1125 * channels so the data will be available as RGBA quartets. 1126 */ 1127 if ((transforms & PNG_TRANSFORM_EXPAND) != 0) 1128 #ifdef PNG_READ_EXPAND_SUPPORTED 1129 png_set_expand(png_ptr); 1130 #else 1131 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported"); 1132 #endif 1133 1134 /* We don't handle background color or gamma transformation or quantizing. 1135 */ 1136 1137 /* Invert monochrome files to have 0 as white and 1 as black 1138 */ 1139 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0) 1140 #ifdef PNG_READ_INVERT_SUPPORTED 1141 png_set_invert_mono(png_ptr); 1142 #else 1143 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported"); 1144 #endif 1145 1146 /* If you want to shift the pixel values from the range [0,255] or 1147 * [0,65535] to the original [0,7] or [0,31], or whatever range the 1148 * colors were originally in: 1149 */ 1150 if ((transforms & PNG_TRANSFORM_SHIFT) != 0) 1151 #ifdef PNG_READ_SHIFT_SUPPORTED 1152 if ((info_ptr->valid & PNG_INFO_sBIT) != 0) 1153 png_set_shift(png_ptr, &info_ptr->sig_bit); 1154 #else 1155 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported"); 1156 #endif 1157 1158 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */ 1159 if ((transforms & PNG_TRANSFORM_BGR) != 0) 1160 #ifdef PNG_READ_BGR_SUPPORTED 1161 png_set_bgr(png_ptr); 1162 #else 1163 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported"); 1164 #endif 1165 1166 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ 1167 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0) 1168 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED 1169 png_set_swap_alpha(png_ptr); 1170 #else 1171 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported"); 1172 #endif 1173 1174 /* Swap bytes of 16-bit files to least significant byte first */ 1175 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0) 1176 #ifdef PNG_READ_SWAP_SUPPORTED 1177 png_set_swap(png_ptr); 1178 #else 1179 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported"); 1180 #endif 1181 1182 /* Added at libpng-1.2.41 */ 1183 /* Invert the alpha channel from opacity to transparency */ 1184 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0) 1185 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED 1186 png_set_invert_alpha(png_ptr); 1187 #else 1188 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported"); 1189 #endif 1190 1191 /* Added at libpng-1.2.41 */ 1192 /* Expand grayscale image to RGB */ 1193 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0) 1194 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED 1195 png_set_gray_to_rgb(png_ptr); 1196 #else 1197 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported"); 1198 #endif 1199 1200 /* Added at libpng-1.5.4 */ 1201 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0) 1202 #ifdef PNG_READ_EXPAND_16_SUPPORTED 1203 png_set_expand_16(png_ptr); 1204 #else 1205 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported"); 1206 #endif 1207 1208 /* We don't handle adding filler bytes */ 1209 1210 /* We use png_read_image and rely on that for interlace handling, but we also 1211 * call png_read_update_info therefore must turn on interlace handling now: 1212 */ 1213 (void)png_set_interlace_handling(png_ptr); 1214 1215 /* Optional call to gamma correct and add the background to the palette 1216 * and update info structure. REQUIRED if you are expecting libpng to 1217 * update the palette for you (i.e., you selected such a transform above). 1218 */ 1219 png_read_update_info(png_ptr, info_ptr); 1220 1221 /* -------------- image transformations end here ------------------- */ 1222 1223 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0); 1224 if (info_ptr->row_pointers == NULL) 1225 { 1226 png_uint_32 iptr; 1227 1228 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr, 1229 info_ptr->height * (sizeof (png_bytep)))); 1230 1231 for (iptr=0; iptr<info_ptr->height; iptr++) 1232 info_ptr->row_pointers[iptr] = NULL; 1233 1234 info_ptr->free_me |= PNG_FREE_ROWS; 1235 1236 for (iptr = 0; iptr < info_ptr->height; iptr++) 1237 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep, 1238 png_malloc(png_ptr, info_ptr->rowbytes)); 1239 } 1240 1241 png_read_image(png_ptr, info_ptr->row_pointers); 1242 info_ptr->valid |= PNG_INFO_IDAT; 1243 1244 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */ 1245 png_read_end(png_ptr, info_ptr); 1246 1247 PNG_UNUSED(params) 1248 } 1249 #endif /* INFO_IMAGE */ 1250 #endif /* SEQUENTIAL_READ */ 1251 1252 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED 1253 /* SIMPLIFIED READ 1254 * 1255 * This code currently relies on the sequential reader, though it could easily 1256 * be made to work with the progressive one. 1257 */ 1258 /* Arguments to png_image_finish_read: */ 1259 1260 /* Encoding of PNG data (used by the color-map code) */ 1261 # define P_NOTSET 0 /* File encoding not yet known */ 1262 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */ 1263 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */ 1264 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */ 1265 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */ 1266 1267 /* Color-map processing: after libpng has run on the PNG image further 1268 * processing may be needed to convert the data to color-map indices. 1269 */ 1270 #define PNG_CMAP_NONE 0 1271 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */ 1272 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */ 1273 #define PNG_CMAP_RGB 3 /* Process RGB data */ 1274 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */ 1275 1276 /* The following document where the background is for each processing case. */ 1277 #define PNG_CMAP_NONE_BACKGROUND 256 1278 #define PNG_CMAP_GA_BACKGROUND 231 1279 #define PNG_CMAP_TRANS_BACKGROUND 254 1280 #define PNG_CMAP_RGB_BACKGROUND 256 1281 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216 1282 1283 typedef struct 1284 { 1285 /* Arguments: */ 1286 png_imagep image; 1287 png_voidp buffer; 1288 png_int_32 row_stride; 1289 png_voidp colormap; 1290 png_const_colorp background; 1291 /* Local variables: */ 1292 png_voidp local_row; 1293 png_voidp first_row; 1294 ptrdiff_t row_bytes; /* step between rows */ 1295 int file_encoding; /* E_ values above */ 1296 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */ 1297 int colormap_processing; /* PNG_CMAP_ values above */ 1298 } png_image_read_control; 1299 1300 /* Do all the *safe* initialization - 'safe' means that png_error won't be 1301 * called, so setting up the jmp_buf is not required. This means that anything 1302 * called from here must *not* call png_malloc - it has to call png_malloc_warn 1303 * instead so that control is returned safely back to this routine. 1304 */ 1305 static int 1306 png_image_read_init(png_imagep image) 1307 { 1308 if (image->opaque == NULL) 1309 { 1310 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image, 1311 png_safe_error, png_safe_warning); 1312 1313 /* And set the rest of the structure to NULL to ensure that the various 1314 * fields are consistent. 1315 */ 1316 memset(image, 0, (sizeof *image)); 1317 image->version = PNG_IMAGE_VERSION; 1318 1319 if (png_ptr != NULL) 1320 { 1321 png_infop info_ptr = png_create_info_struct(png_ptr); 1322 1323 if (info_ptr != NULL) 1324 { 1325 png_controlp control = png_voidcast(png_controlp, 1326 png_malloc_warn(png_ptr, (sizeof *control))); 1327 1328 if (control != NULL) 1329 { 1330 memset(control, 0, (sizeof *control)); 1331 1332 control->png_ptr = png_ptr; 1333 control->info_ptr = info_ptr; 1334 control->for_write = 0; 1335 1336 image->opaque = control; 1337 return 1; 1338 } 1339 1340 /* Error clean up */ 1341 png_destroy_info_struct(png_ptr, &info_ptr); 1342 } 1343 1344 png_destroy_read_struct(&png_ptr, NULL, NULL); 1345 } 1346 1347 return png_image_error(image, "png_image_read: out of memory"); 1348 } 1349 1350 return png_image_error(image, "png_image_read: opaque pointer not NULL"); 1351 } 1352 1353 /* Utility to find the base format of a PNG file from a png_struct. */ 1354 static png_uint_32 1355 png_image_format(png_structrp png_ptr) 1356 { 1357 png_uint_32 format = 0; 1358 1359 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0) 1360 format |= PNG_FORMAT_FLAG_COLOR; 1361 1362 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0) 1363 format |= PNG_FORMAT_FLAG_ALPHA; 1364 1365 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS 1366 * sets the png_struct fields; that's all we are interested in here. The 1367 * precise interaction with an app call to png_set_tRNS and PNG file reading 1368 * is unclear. 1369 */ 1370 else if (png_ptr->num_trans > 0) 1371 format |= PNG_FORMAT_FLAG_ALPHA; 1372 1373 if (png_ptr->bit_depth == 16) 1374 format |= PNG_FORMAT_FLAG_LINEAR; 1375 1376 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0) 1377 format |= PNG_FORMAT_FLAG_COLORMAP; 1378 1379 return format; 1380 } 1381 1382 /* Is the given gamma significantly different from sRGB? The test is the same 1383 * one used in pngrtran.c when deciding whether to do gamma correction. The 1384 * arithmetic optimizes the division by using the fact that the inverse of the 1385 * file sRGB gamma is 2.2 1386 */ 1387 static int 1388 png_gamma_not_sRGB(png_fixed_point g) 1389 { 1390 if (g < PNG_FP_1) 1391 { 1392 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */ 1393 if (g == 0) 1394 return 0; 1395 1396 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */); 1397 } 1398 1399 return 1; 1400 } 1401 1402 /* Do the main body of a 'png_image_begin_read' function; read the PNG file 1403 * header and fill in all the information. This is executed in a safe context, 1404 * unlike the init routine above. 1405 */ 1406 static int 1407 png_image_read_header(png_voidp argument) 1408 { 1409 png_imagep image = png_voidcast(png_imagep, argument); 1410 png_structrp png_ptr = image->opaque->png_ptr; 1411 png_inforp info_ptr = image->opaque->info_ptr; 1412 1413 #ifdef PNG_BENIGN_ERRORS_SUPPORTED 1414 png_set_benign_errors(png_ptr, 1/*warn*/); 1415 #endif 1416 png_read_info(png_ptr, info_ptr); 1417 1418 /* Do this the fast way; just read directly out of png_struct. */ 1419 image->width = png_ptr->width; 1420 image->height = png_ptr->height; 1421 1422 { 1423 png_uint_32 format = png_image_format(png_ptr); 1424 1425 image->format = format; 1426 1427 #ifdef PNG_COLORSPACE_SUPPORTED 1428 /* Does the colorspace match sRGB? If there is no color endpoint 1429 * (colorant) information assume yes, otherwise require the 1430 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the 1431 * colorspace has been determined to be invalid ignore it. 1432 */ 1433 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags 1434 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB| 1435 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS)) 1436 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB; 1437 #endif 1438 } 1439 1440 /* We need the maximum number of entries regardless of the format the 1441 * application sets here. 1442 */ 1443 { 1444 png_uint_32 cmap_entries; 1445 1446 switch (png_ptr->color_type) 1447 { 1448 case PNG_COLOR_TYPE_GRAY: 1449 cmap_entries = 1U << png_ptr->bit_depth; 1450 break; 1451 1452 case PNG_COLOR_TYPE_PALETTE: 1453 cmap_entries = (png_uint_32)png_ptr->num_palette; 1454 break; 1455 1456 default: 1457 cmap_entries = 256; 1458 break; 1459 } 1460 1461 if (cmap_entries > 256) 1462 cmap_entries = 256; 1463 1464 image->colormap_entries = cmap_entries; 1465 } 1466 1467 return 1; 1468 } 1469 1470 #ifdef PNG_STDIO_SUPPORTED 1471 int PNGAPI 1472 png_image_begin_read_from_stdio(png_imagep image, FILE* file) 1473 { 1474 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1475 { 1476 if (file != NULL) 1477 { 1478 if (png_image_read_init(image) != 0) 1479 { 1480 /* This is slightly evil, but png_init_io doesn't do anything other 1481 * than this and we haven't changed the standard IO functions so 1482 * this saves a 'safe' function. 1483 */ 1484 image->opaque->png_ptr->io_ptr = file; 1485 return png_safe_execute(image, png_image_read_header, image); 1486 } 1487 } 1488 1489 else 1490 return png_image_error(image, 1491 "png_image_begin_read_from_stdio: invalid argument"); 1492 } 1493 1494 else if (image != NULL) 1495 return png_image_error(image, 1496 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION"); 1497 1498 return 0; 1499 } 1500 1501 int PNGAPI 1502 png_image_begin_read_from_file(png_imagep image, const char *file_name) 1503 { 1504 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1505 { 1506 if (file_name != NULL) 1507 { 1508 FILE *fp = fopen(file_name, "rb"); 1509 1510 if (fp != NULL) 1511 { 1512 if (png_image_read_init(image) != 0) 1513 { 1514 image->opaque->png_ptr->io_ptr = fp; 1515 image->opaque->owned_file = 1; 1516 return png_safe_execute(image, png_image_read_header, image); 1517 } 1518 1519 /* Clean up: just the opened file. */ 1520 (void)fclose(fp); 1521 } 1522 1523 else 1524 return png_image_error(image, strerror(errno)); 1525 } 1526 1527 else 1528 return png_image_error(image, 1529 "png_image_begin_read_from_file: invalid argument"); 1530 } 1531 1532 else if (image != NULL) 1533 return png_image_error(image, 1534 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION"); 1535 1536 return 0; 1537 } 1538 #endif /* STDIO */ 1539 1540 static void PNGCBAPI 1541 png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need) 1542 { 1543 if (png_ptr != NULL) 1544 { 1545 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr); 1546 if (image != NULL) 1547 { 1548 png_controlp cp = image->opaque; 1549 if (cp != NULL) 1550 { 1551 png_const_bytep memory = cp->memory; 1552 size_t size = cp->size; 1553 1554 if (memory != NULL && size >= need) 1555 { 1556 memcpy(out, memory, need); 1557 cp->memory = memory + need; 1558 cp->size = size - need; 1559 return; 1560 } 1561 1562 png_error(png_ptr, "read beyond end of data"); 1563 } 1564 } 1565 1566 png_error(png_ptr, "invalid memory read"); 1567 } 1568 } 1569 1570 int PNGAPI png_image_begin_read_from_memory(png_imagep image, 1571 png_const_voidp memory, size_t size) 1572 { 1573 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1574 { 1575 if (memory != NULL && size > 0) 1576 { 1577 if (png_image_read_init(image) != 0) 1578 { 1579 /* Now set the IO functions to read from the memory buffer and 1580 * store it into io_ptr. Again do this in-place to avoid calling a 1581 * libpng function that requires error handling. 1582 */ 1583 image->opaque->memory = png_voidcast(png_const_bytep, memory); 1584 image->opaque->size = size; 1585 image->opaque->png_ptr->io_ptr = image; 1586 image->opaque->png_ptr->read_data_fn = png_image_memory_read; 1587 1588 return png_safe_execute(image, png_image_read_header, image); 1589 } 1590 } 1591 1592 else 1593 return png_image_error(image, 1594 "png_image_begin_read_from_memory: invalid argument"); 1595 } 1596 1597 else if (image != NULL) 1598 return png_image_error(image, 1599 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION"); 1600 1601 return 0; 1602 } 1603 1604 /* Utility function to skip chunks that are not used by the simplified image 1605 * read functions and an appropriate macro to call it. 1606 */ 1607 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 1608 static void 1609 png_image_skip_unused_chunks(png_structrp png_ptr) 1610 { 1611 /* Prepare the reader to ignore all recognized chunks whose data will not 1612 * be used, i.e., all chunks recognized by libpng except for those 1613 * involved in basic image reading: 1614 * 1615 * IHDR, PLTE, IDAT, IEND 1616 * 1617 * Or image data handling: 1618 * 1619 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT. 1620 * 1621 * This provides a small performance improvement and eliminates any 1622 * potential vulnerability to security problems in the unused chunks. 1623 * 1624 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored 1625 * too. This allows the simplified API to be compiled without iCCP support, 1626 * however if the support is there the chunk is still checked to detect 1627 * errors (which are unfortunately quite common.) 1628 */ 1629 { 1630 static const png_byte chunks_to_process[] = { 1631 98, 75, 71, 68, '\0', /* bKGD */ 1632 99, 72, 82, 77, '\0', /* cHRM */ 1633 103, 65, 77, 65, '\0', /* gAMA */ 1634 # ifdef PNG_READ_iCCP_SUPPORTED 1635 105, 67, 67, 80, '\0', /* iCCP */ 1636 # endif 1637 115, 66, 73, 84, '\0', /* sBIT */ 1638 115, 82, 71, 66, '\0', /* sRGB */ 1639 }; 1640 1641 /* Ignore unknown chunks and all other chunks except for the 1642 * IHDR, PLTE, tRNS, IDAT, and IEND chunks. 1643 */ 1644 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER, 1645 NULL, -1); 1646 1647 /* But do not ignore image data handling chunks */ 1648 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT, 1649 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5); 1650 } 1651 } 1652 1653 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p) 1654 #else 1655 # define PNG_SKIP_CHUNKS(p) ((void)0) 1656 #endif /* HANDLE_AS_UNKNOWN */ 1657 1658 /* The following macro gives the exact rounded answer for all values in the 1659 * range 0..255 (it actually divides by 51.2, but the rounding still generates 1660 * the correct numbers 0..5 1661 */ 1662 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8) 1663 1664 /* Utility functions to make particular color-maps */ 1665 static void 1666 set_file_encoding(png_image_read_control *display) 1667 { 1668 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma; 1669 if (png_gamma_significant(g) != 0) 1670 { 1671 if (png_gamma_not_sRGB(g) != 0) 1672 { 1673 display->file_encoding = P_FILE; 1674 display->gamma_to_linear = png_reciprocal(g); 1675 } 1676 1677 else 1678 display->file_encoding = P_sRGB; 1679 } 1680 1681 else 1682 display->file_encoding = P_LINEAR8; 1683 } 1684 1685 static unsigned int 1686 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding) 1687 { 1688 if (encoding == P_FILE) /* double check */ 1689 encoding = display->file_encoding; 1690 1691 if (encoding == P_NOTSET) /* must be the file encoding */ 1692 { 1693 set_file_encoding(display); 1694 encoding = display->file_encoding; 1695 } 1696 1697 switch (encoding) 1698 { 1699 case P_FILE: 1700 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear); 1701 break; 1702 1703 case P_sRGB: 1704 value = png_sRGB_table[value]; 1705 break; 1706 1707 case P_LINEAR: 1708 break; 1709 1710 case P_LINEAR8: 1711 value *= 257; 1712 break; 1713 1714 #ifdef __GNUC__ 1715 default: 1716 png_error(display->image->opaque->png_ptr, 1717 "unexpected encoding (internal error)"); 1718 #endif 1719 } 1720 1721 return value; 1722 } 1723 1724 static png_uint_32 1725 png_colormap_compose(png_image_read_control *display, 1726 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha, 1727 png_uint_32 background, int encoding) 1728 { 1729 /* The file value is composed on the background, the background has the given 1730 * encoding and so does the result, the file is encoded with P_FILE and the 1731 * file and alpha are 8-bit values. The (output) encoding will always be 1732 * P_LINEAR or P_sRGB. 1733 */ 1734 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding); 1735 png_uint_32 b = decode_gamma(display, background, encoding); 1736 1737 /* The alpha is always an 8-bit value (it comes from the palette), the value 1738 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires. 1739 */ 1740 f = f * alpha + b * (255-alpha); 1741 1742 if (encoding == P_LINEAR) 1743 { 1744 /* Scale to 65535; divide by 255, approximately (in fact this is extremely 1745 * accurate, it divides by 255.00000005937181414556, with no overflow.) 1746 */ 1747 f *= 257; /* Now scaled by 65535 */ 1748 f += f >> 16; 1749 f = (f+32768) >> 16; 1750 } 1751 1752 else /* P_sRGB */ 1753 f = PNG_sRGB_FROM_LINEAR(f); 1754 1755 return f; 1756 } 1757 1758 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must 1759 * be 8-bit. 1760 */ 1761 static void 1762 png_create_colormap_entry(png_image_read_control *display, 1763 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue, 1764 png_uint_32 alpha, int encoding) 1765 { 1766 png_imagep image = display->image; 1767 int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ? 1768 P_LINEAR : P_sRGB; 1769 int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 && 1770 (red != green || green != blue); 1771 1772 if (ip > 255) 1773 png_error(image->opaque->png_ptr, "color-map index out of range"); 1774 1775 /* Update the cache with whether the file gamma is significantly different 1776 * from sRGB. 1777 */ 1778 if (encoding == P_FILE) 1779 { 1780 if (display->file_encoding == P_NOTSET) 1781 set_file_encoding(display); 1782 1783 /* Note that the cached value may be P_FILE too, but if it is then the 1784 * gamma_to_linear member has been set. 1785 */ 1786 encoding = display->file_encoding; 1787 } 1788 1789 if (encoding == P_FILE) 1790 { 1791 png_fixed_point g = display->gamma_to_linear; 1792 1793 red = png_gamma_16bit_correct(red*257, g); 1794 green = png_gamma_16bit_correct(green*257, g); 1795 blue = png_gamma_16bit_correct(blue*257, g); 1796 1797 if (convert_to_Y != 0 || output_encoding == P_LINEAR) 1798 { 1799 alpha *= 257; 1800 encoding = P_LINEAR; 1801 } 1802 1803 else 1804 { 1805 red = PNG_sRGB_FROM_LINEAR(red * 255); 1806 green = PNG_sRGB_FROM_LINEAR(green * 255); 1807 blue = PNG_sRGB_FROM_LINEAR(blue * 255); 1808 encoding = P_sRGB; 1809 } 1810 } 1811 1812 else if (encoding == P_LINEAR8) 1813 { 1814 /* This encoding occurs quite frequently in test cases because PngSuite 1815 * includes a gAMA 1.0 chunk with most images. 1816 */ 1817 red *= 257; 1818 green *= 257; 1819 blue *= 257; 1820 alpha *= 257; 1821 encoding = P_LINEAR; 1822 } 1823 1824 else if (encoding == P_sRGB && 1825 (convert_to_Y != 0 || output_encoding == P_LINEAR)) 1826 { 1827 /* The values are 8-bit sRGB values, but must be converted to 16-bit 1828 * linear. 1829 */ 1830 red = png_sRGB_table[red]; 1831 green = png_sRGB_table[green]; 1832 blue = png_sRGB_table[blue]; 1833 alpha *= 257; 1834 encoding = P_LINEAR; 1835 } 1836 1837 /* This is set if the color isn't gray but the output is. */ 1838 if (encoding == P_LINEAR) 1839 { 1840 if (convert_to_Y != 0) 1841 { 1842 /* NOTE: these values are copied from png_do_rgb_to_gray */ 1843 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green + 1844 (png_uint_32)2366 * blue; 1845 1846 if (output_encoding == P_LINEAR) 1847 y = (y + 16384) >> 15; 1848 1849 else 1850 { 1851 /* y is scaled by 32768, we need it scaled by 255: */ 1852 y = (y + 128) >> 8; 1853 y *= 255; 1854 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7); 1855 alpha = PNG_DIV257(alpha); 1856 encoding = P_sRGB; 1857 } 1858 1859 blue = red = green = y; 1860 } 1861 1862 else if (output_encoding == P_sRGB) 1863 { 1864 red = PNG_sRGB_FROM_LINEAR(red * 255); 1865 green = PNG_sRGB_FROM_LINEAR(green * 255); 1866 blue = PNG_sRGB_FROM_LINEAR(blue * 255); 1867 alpha = PNG_DIV257(alpha); 1868 encoding = P_sRGB; 1869 } 1870 } 1871 1872 if (encoding != output_encoding) 1873 png_error(image->opaque->png_ptr, "bad encoding (internal error)"); 1874 1875 /* Store the value. */ 1876 { 1877 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 1878 int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 && 1879 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0; 1880 # else 1881 # define afirst 0 1882 # endif 1883 # ifdef PNG_FORMAT_BGR_SUPPORTED 1884 int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0; 1885 # else 1886 # define bgr 0 1887 # endif 1888 1889 if (output_encoding == P_LINEAR) 1890 { 1891 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap); 1892 1893 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format); 1894 1895 /* The linear 16-bit values must be pre-multiplied by the alpha channel 1896 * value, if less than 65535 (this is, effectively, composite on black 1897 * if the alpha channel is removed.) 1898 */ 1899 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format)) 1900 { 1901 case 4: 1902 entry[afirst ? 0 : 3] = (png_uint_16)alpha; 1903 /* FALLTHROUGH */ 1904 1905 case 3: 1906 if (alpha < 65535) 1907 { 1908 if (alpha > 0) 1909 { 1910 blue = (blue * alpha + 32767U)/65535U; 1911 green = (green * alpha + 32767U)/65535U; 1912 red = (red * alpha + 32767U)/65535U; 1913 } 1914 1915 else 1916 red = green = blue = 0; 1917 } 1918 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue; 1919 entry[afirst + 1] = (png_uint_16)green; 1920 entry[afirst + bgr] = (png_uint_16)red; 1921 break; 1922 1923 case 2: 1924 entry[1 ^ afirst] = (png_uint_16)alpha; 1925 /* FALLTHROUGH */ 1926 1927 case 1: 1928 if (alpha < 65535) 1929 { 1930 if (alpha > 0) 1931 green = (green * alpha + 32767U)/65535U; 1932 1933 else 1934 green = 0; 1935 } 1936 entry[afirst] = (png_uint_16)green; 1937 break; 1938 1939 default: 1940 break; 1941 } 1942 } 1943 1944 else /* output encoding is P_sRGB */ 1945 { 1946 png_bytep entry = png_voidcast(png_bytep, display->colormap); 1947 1948 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format); 1949 1950 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format)) 1951 { 1952 case 4: 1953 entry[afirst ? 0 : 3] = (png_byte)alpha; 1954 /* FALLTHROUGH */ 1955 case 3: 1956 entry[afirst + (2 ^ bgr)] = (png_byte)blue; 1957 entry[afirst + 1] = (png_byte)green; 1958 entry[afirst + bgr] = (png_byte)red; 1959 break; 1960 1961 case 2: 1962 entry[1 ^ afirst] = (png_byte)alpha; 1963 /* FALLTHROUGH */ 1964 case 1: 1965 entry[afirst] = (png_byte)green; 1966 break; 1967 1968 default: 1969 break; 1970 } 1971 } 1972 1973 # ifdef afirst 1974 # undef afirst 1975 # endif 1976 # ifdef bgr 1977 # undef bgr 1978 # endif 1979 } 1980 } 1981 1982 static int 1983 make_gray_file_colormap(png_image_read_control *display) 1984 { 1985 unsigned int i; 1986 1987 for (i=0; i<256; ++i) 1988 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE); 1989 1990 return (int)i; 1991 } 1992 1993 static int 1994 make_gray_colormap(png_image_read_control *display) 1995 { 1996 unsigned int i; 1997 1998 for (i=0; i<256; ++i) 1999 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB); 2000 2001 return (int)i; 2002 } 2003 #define PNG_GRAY_COLORMAP_ENTRIES 256 2004 2005 static int 2006 make_ga_colormap(png_image_read_control *display) 2007 { 2008 unsigned int i, a; 2009 2010 /* Alpha is retained, the output will be a color-map with entries 2011 * selected by six levels of alpha. One transparent entry, 6 gray 2012 * levels for all the intermediate alpha values, leaving 230 entries 2013 * for the opaque grays. The color-map entries are the six values 2014 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the 2015 * relevant entry. 2016 * 2017 * if (alpha > 229) // opaque 2018 * { 2019 * // The 231 entries are selected to make the math below work: 2020 * base = 0; 2021 * entry = (231 * gray + 128) >> 8; 2022 * } 2023 * else if (alpha < 26) // transparent 2024 * { 2025 * base = 231; 2026 * entry = 0; 2027 * } 2028 * else // partially opaque 2029 * { 2030 * base = 226 + 6 * PNG_DIV51(alpha); 2031 * entry = PNG_DIV51(gray); 2032 * } 2033 */ 2034 i = 0; 2035 while (i < 231) 2036 { 2037 unsigned int gray = (i * 256 + 115) / 231; 2038 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB); 2039 } 2040 2041 /* 255 is used here for the component values for consistency with the code 2042 * that undoes premultiplication in pngwrite.c. 2043 */ 2044 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB); 2045 2046 for (a=1; a<5; ++a) 2047 { 2048 unsigned int g; 2049 2050 for (g=0; g<6; ++g) 2051 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51, 2052 P_sRGB); 2053 } 2054 2055 return (int)i; 2056 } 2057 2058 #define PNG_GA_COLORMAP_ENTRIES 256 2059 2060 static int 2061 make_rgb_colormap(png_image_read_control *display) 2062 { 2063 unsigned int i, r; 2064 2065 /* Build a 6x6x6 opaque RGB cube */ 2066 for (i=r=0; r<6; ++r) 2067 { 2068 unsigned int g; 2069 2070 for (g=0; g<6; ++g) 2071 { 2072 unsigned int b; 2073 2074 for (b=0; b<6; ++b) 2075 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255, 2076 P_sRGB); 2077 } 2078 } 2079 2080 return (int)i; 2081 } 2082 2083 #define PNG_RGB_COLORMAP_ENTRIES 216 2084 2085 /* Return a palette index to the above palette given three 8-bit sRGB values. */ 2086 #define PNG_RGB_INDEX(r,g,b) \ 2087 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b))) 2088 2089 static int 2090 png_image_read_colormap(png_voidp argument) 2091 { 2092 png_image_read_control *display = 2093 png_voidcast(png_image_read_control*, argument); 2094 png_imagep image = display->image; 2095 2096 png_structrp png_ptr = image->opaque->png_ptr; 2097 png_uint_32 output_format = image->format; 2098 int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ? 2099 P_LINEAR : P_sRGB; 2100 2101 unsigned int cmap_entries; 2102 unsigned int output_processing; /* Output processing option */ 2103 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */ 2104 2105 /* Background information; the background color and the index of this color 2106 * in the color-map if it exists (else 256). 2107 */ 2108 unsigned int background_index = 256; 2109 png_uint_32 back_r, back_g, back_b; 2110 2111 /* Flags to accumulate things that need to be done to the input. */ 2112 int expand_tRNS = 0; 2113 2114 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is 2115 * very difficult to do, the results look awful, and it is difficult to see 2116 * what possible use it is because the application can't control the 2117 * color-map. 2118 */ 2119 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 || 2120 png_ptr->num_trans > 0) /* alpha in input */ && 2121 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */) 2122 { 2123 if (output_encoding == P_LINEAR) /* compose on black */ 2124 back_b = back_g = back_r = 0; 2125 2126 else if (display->background == NULL /* no way to remove it */) 2127 png_error(png_ptr, 2128 "background color must be supplied to remove alpha/transparency"); 2129 2130 /* Get a copy of the background color (this avoids repeating the checks 2131 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the 2132 * output format. 2133 */ 2134 else 2135 { 2136 back_g = display->background->green; 2137 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0) 2138 { 2139 back_r = display->background->red; 2140 back_b = display->background->blue; 2141 } 2142 else 2143 back_b = back_r = back_g; 2144 } 2145 } 2146 2147 else if (output_encoding == P_LINEAR) 2148 back_b = back_r = back_g = 65535; 2149 2150 else 2151 back_b = back_r = back_g = 255; 2152 2153 /* Default the input file gamma if required - this is necessary because 2154 * libpng assumes that if no gamma information is present the data is in the 2155 * output format, but the simplified API deduces the gamma from the input 2156 * format. 2157 */ 2158 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0) 2159 { 2160 /* Do this directly, not using the png_colorspace functions, to ensure 2161 * that it happens even if the colorspace is invalid (though probably if 2162 * it is the setting will be ignored) Note that the same thing can be 2163 * achieved at the application interface with png_set_gAMA. 2164 */ 2165 if (png_ptr->bit_depth == 16 && 2166 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0) 2167 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR; 2168 2169 else 2170 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE; 2171 2172 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA; 2173 } 2174 2175 /* Decide what to do based on the PNG color type of the input data. The 2176 * utility function png_create_colormap_entry deals with most aspects of the 2177 * output transformations; this code works out how to produce bytes of 2178 * color-map entries from the original format. 2179 */ 2180 switch (png_ptr->color_type) 2181 { 2182 case PNG_COLOR_TYPE_GRAY: 2183 if (png_ptr->bit_depth <= 8) 2184 { 2185 /* There at most 256 colors in the output, regardless of 2186 * transparency. 2187 */ 2188 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0; 2189 2190 cmap_entries = 1U << png_ptr->bit_depth; 2191 if (cmap_entries > image->colormap_entries) 2192 png_error(png_ptr, "gray[8] color-map: too few entries"); 2193 2194 step = 255 / (cmap_entries - 1); 2195 output_processing = PNG_CMAP_NONE; 2196 2197 /* If there is a tRNS chunk then this either selects a transparent 2198 * value or, if the output has no alpha, the background color. 2199 */ 2200 if (png_ptr->num_trans > 0) 2201 { 2202 trans = png_ptr->trans_color.gray; 2203 2204 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) 2205 back_alpha = output_encoding == P_LINEAR ? 65535 : 255; 2206 } 2207 2208 /* png_create_colormap_entry just takes an RGBA and writes the 2209 * corresponding color-map entry using the format from 'image', 2210 * including the required conversion to sRGB or linear as 2211 * appropriate. The input values are always either sRGB (if the 2212 * gamma correction flag is 0) or 0..255 scaled file encoded values 2213 * (if the function must gamma correct them). 2214 */ 2215 for (i=val=0; i<cmap_entries; ++i, val += step) 2216 { 2217 /* 'i' is a file value. While this will result in duplicated 2218 * entries for 8-bit non-sRGB encoded files it is necessary to 2219 * have non-gamma corrected values to do tRNS handling. 2220 */ 2221 if (i != trans) 2222 png_create_colormap_entry(display, i, val, val, val, 255, 2223 P_FILE/*8-bit with file gamma*/); 2224 2225 /* Else this entry is transparent. The colors don't matter if 2226 * there is an alpha channel (back_alpha == 0), but it does no 2227 * harm to pass them in; the values are not set above so this 2228 * passes in white. 2229 * 2230 * NOTE: this preserves the full precision of the application 2231 * supplied background color when it is used. 2232 */ 2233 else 2234 png_create_colormap_entry(display, i, back_r, back_g, back_b, 2235 back_alpha, output_encoding); 2236 } 2237 2238 /* We need libpng to preserve the original encoding. */ 2239 data_encoding = P_FILE; 2240 2241 /* The rows from libpng, while technically gray values, are now also 2242 * color-map indices; however, they may need to be expanded to 1 2243 * byte per pixel. This is what png_set_packing does (i.e., it 2244 * unpacks the bit values into bytes.) 2245 */ 2246 if (png_ptr->bit_depth < 8) 2247 png_set_packing(png_ptr); 2248 } 2249 2250 else /* bit depth is 16 */ 2251 { 2252 /* The 16-bit input values can be converted directly to 8-bit gamma 2253 * encoded values; however, if a tRNS chunk is present 257 color-map 2254 * entries are required. This means that the extra entry requires 2255 * special processing; add an alpha channel, sacrifice gray level 2256 * 254 and convert transparent (alpha==0) entries to that. 2257 * 2258 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the 2259 * same time to minimize quality loss. If a tRNS chunk is present 2260 * this means libpng must handle it too; otherwise it is impossible 2261 * to do the exact match on the 16-bit value. 2262 * 2263 * If the output has no alpha channel *and* the background color is 2264 * gray then it is possible to let libpng handle the substitution by 2265 * ensuring that the corresponding gray level matches the background 2266 * color exactly. 2267 */ 2268 data_encoding = P_sRGB; 2269 2270 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2271 png_error(png_ptr, "gray[16] color-map: too few entries"); 2272 2273 cmap_entries = (unsigned int)make_gray_colormap(display); 2274 2275 if (png_ptr->num_trans > 0) 2276 { 2277 unsigned int back_alpha; 2278 2279 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0) 2280 back_alpha = 0; 2281 2282 else 2283 { 2284 if (back_r == back_g && back_g == back_b) 2285 { 2286 /* Background is gray; no special processing will be 2287 * required. 2288 */ 2289 png_color_16 c; 2290 png_uint_32 gray = back_g; 2291 2292 if (output_encoding == P_LINEAR) 2293 { 2294 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2295 2296 /* And make sure the corresponding palette entry 2297 * matches. 2298 */ 2299 png_create_colormap_entry(display, gray, back_g, back_g, 2300 back_g, 65535, P_LINEAR); 2301 } 2302 2303 /* The background passed to libpng, however, must be the 2304 * sRGB value. 2305 */ 2306 c.index = 0; /*unused*/ 2307 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2308 2309 /* NOTE: does this work without expanding tRNS to alpha? 2310 * It should be the color->gray case below apparently 2311 * doesn't. 2312 */ 2313 png_set_background_fixed(png_ptr, &c, 2314 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2315 0/*gamma: not used*/); 2316 2317 output_processing = PNG_CMAP_NONE; 2318 break; 2319 } 2320 #ifdef __COVERITY__ 2321 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR) 2322 * here. 2323 */ 2324 back_alpha = 255; 2325 #else 2326 back_alpha = output_encoding == P_LINEAR ? 65535 : 255; 2327 #endif 2328 } 2329 2330 /* output_processing means that the libpng-processed row will be 2331 * 8-bit GA and it has to be processing to single byte color-map 2332 * values. Entry 254 is replaced by either a completely 2333 * transparent entry or by the background color at full 2334 * precision (and the background color is not a simple gray 2335 * level in this case.) 2336 */ 2337 expand_tRNS = 1; 2338 output_processing = PNG_CMAP_TRANS; 2339 background_index = 254; 2340 2341 /* And set (overwrite) color-map entry 254 to the actual 2342 * background color at full precision. 2343 */ 2344 png_create_colormap_entry(display, 254, back_r, back_g, back_b, 2345 back_alpha, output_encoding); 2346 } 2347 2348 else 2349 output_processing = PNG_CMAP_NONE; 2350 } 2351 break; 2352 2353 case PNG_COLOR_TYPE_GRAY_ALPHA: 2354 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum 2355 * of 65536 combinations. If, however, the alpha channel is to be 2356 * removed there are only 256 possibilities if the background is gray. 2357 * (Otherwise there is a subset of the 65536 possibilities defined by 2358 * the triangle between black, white and the background color.) 2359 * 2360 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to 2361 * worry about tRNS matching - tRNS is ignored if there is an alpha 2362 * channel. 2363 */ 2364 data_encoding = P_sRGB; 2365 2366 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0) 2367 { 2368 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2369 png_error(png_ptr, "gray+alpha color-map: too few entries"); 2370 2371 cmap_entries = (unsigned int)make_ga_colormap(display); 2372 2373 background_index = PNG_CMAP_GA_BACKGROUND; 2374 output_processing = PNG_CMAP_GA; 2375 } 2376 2377 else /* alpha is removed */ 2378 { 2379 /* Alpha must be removed as the PNG data is processed when the 2380 * background is a color because the G and A channels are 2381 * independent and the vector addition (non-parallel vectors) is a 2382 * 2-D problem. 2383 * 2384 * This can be reduced to the same algorithm as above by making a 2385 * colormap containing gray levels (for the opaque grays), a 2386 * background entry (for a transparent pixel) and a set of four six 2387 * level color values, one set for each intermediate alpha value. 2388 * See the comments in make_ga_colormap for how this works in the 2389 * per-pixel processing. 2390 * 2391 * If the background is gray, however, we only need a 256 entry gray 2392 * level color map. It is sufficient to make the entry generated 2393 * for the background color be exactly the color specified. 2394 */ 2395 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 || 2396 (back_r == back_g && back_g == back_b)) 2397 { 2398 /* Background is gray; no special processing will be required. */ 2399 png_color_16 c; 2400 png_uint_32 gray = back_g; 2401 2402 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2403 png_error(png_ptr, "gray-alpha color-map: too few entries"); 2404 2405 cmap_entries = (unsigned int)make_gray_colormap(display); 2406 2407 if (output_encoding == P_LINEAR) 2408 { 2409 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2410 2411 /* And make sure the corresponding palette entry matches. */ 2412 png_create_colormap_entry(display, gray, back_g, back_g, 2413 back_g, 65535, P_LINEAR); 2414 } 2415 2416 /* The background passed to libpng, however, must be the sRGB 2417 * value. 2418 */ 2419 c.index = 0; /*unused*/ 2420 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2421 2422 png_set_background_fixed(png_ptr, &c, 2423 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2424 0/*gamma: not used*/); 2425 2426 output_processing = PNG_CMAP_NONE; 2427 } 2428 2429 else 2430 { 2431 png_uint_32 i, a; 2432 2433 /* This is the same as png_make_ga_colormap, above, except that 2434 * the entries are all opaque. 2435 */ 2436 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2437 png_error(png_ptr, "ga-alpha color-map: too few entries"); 2438 2439 i = 0; 2440 while (i < 231) 2441 { 2442 png_uint_32 gray = (i * 256 + 115) / 231; 2443 png_create_colormap_entry(display, i++, gray, gray, gray, 2444 255, P_sRGB); 2445 } 2446 2447 /* NOTE: this preserves the full precision of the application 2448 * background color. 2449 */ 2450 background_index = i; 2451 png_create_colormap_entry(display, i++, back_r, back_g, back_b, 2452 #ifdef __COVERITY__ 2453 /* Coverity claims that output_encoding 2454 * cannot be 2 (P_LINEAR) here. 2455 */ 255U, 2456 #else 2457 output_encoding == P_LINEAR ? 65535U : 255U, 2458 #endif 2459 output_encoding); 2460 2461 /* For non-opaque input composite on the sRGB background - this 2462 * requires inverting the encoding for each component. The input 2463 * is still converted to the sRGB encoding because this is a 2464 * reasonable approximate to the logarithmic curve of human 2465 * visual sensitivity, at least over the narrow range which PNG 2466 * represents. Consequently 'G' is always sRGB encoded, while 2467 * 'A' is linear. We need the linear background colors. 2468 */ 2469 if (output_encoding == P_sRGB) /* else already linear */ 2470 { 2471 /* This may produce a value not exactly matching the 2472 * background, but that's ok because these numbers are only 2473 * used when alpha != 0 2474 */ 2475 back_r = png_sRGB_table[back_r]; 2476 back_g = png_sRGB_table[back_g]; 2477 back_b = png_sRGB_table[back_b]; 2478 } 2479 2480 for (a=1; a<5; ++a) 2481 { 2482 unsigned int g; 2483 2484 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled 2485 * by an 8-bit alpha value (0..255). 2486 */ 2487 png_uint_32 alpha = 51 * a; 2488 png_uint_32 back_rx = (255-alpha) * back_r; 2489 png_uint_32 back_gx = (255-alpha) * back_g; 2490 png_uint_32 back_bx = (255-alpha) * back_b; 2491 2492 for (g=0; g<6; ++g) 2493 { 2494 png_uint_32 gray = png_sRGB_table[g*51] * alpha; 2495 2496 png_create_colormap_entry(display, i++, 2497 PNG_sRGB_FROM_LINEAR(gray + back_rx), 2498 PNG_sRGB_FROM_LINEAR(gray + back_gx), 2499 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB); 2500 } 2501 } 2502 2503 cmap_entries = i; 2504 output_processing = PNG_CMAP_GA; 2505 } 2506 } 2507 break; 2508 2509 case PNG_COLOR_TYPE_RGB: 2510 case PNG_COLOR_TYPE_RGB_ALPHA: 2511 /* Exclude the case where the output is gray; we can always handle this 2512 * with the cases above. 2513 */ 2514 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0) 2515 { 2516 /* The color-map will be grayscale, so we may as well convert the 2517 * input RGB values to a simple grayscale and use the grayscale 2518 * code above. 2519 * 2520 * NOTE: calling this apparently damages the recognition of the 2521 * transparent color in background color handling; call 2522 * png_set_tRNS_to_alpha before png_set_background_fixed. 2523 */ 2524 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1, 2525 -1); 2526 data_encoding = P_sRGB; 2527 2528 /* The output will now be one or two 8-bit gray or gray+alpha 2529 * channels. The more complex case arises when the input has alpha. 2530 */ 2531 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2532 png_ptr->num_trans > 0) && 2533 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0) 2534 { 2535 /* Both input and output have an alpha channel, so no background 2536 * processing is required; just map the GA bytes to the right 2537 * color-map entry. 2538 */ 2539 expand_tRNS = 1; 2540 2541 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2542 png_error(png_ptr, "rgb[ga] color-map: too few entries"); 2543 2544 cmap_entries = (unsigned int)make_ga_colormap(display); 2545 background_index = PNG_CMAP_GA_BACKGROUND; 2546 output_processing = PNG_CMAP_GA; 2547 } 2548 2549 else 2550 { 2551 /* Either the input or the output has no alpha channel, so there 2552 * will be no non-opaque pixels in the color-map; it will just be 2553 * grayscale. 2554 */ 2555 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2556 png_error(png_ptr, "rgb[gray] color-map: too few entries"); 2557 2558 /* Ideally this code would use libpng to do the gamma correction, 2559 * but if an input alpha channel is to be removed we will hit the 2560 * libpng bug in gamma+compose+rgb-to-gray (the double gamma 2561 * correction bug). Fix this by dropping the gamma correction in 2562 * this case and doing it in the palette; this will result in 2563 * duplicate palette entries, but that's better than the 2564 * alternative of double gamma correction. 2565 */ 2566 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2567 png_ptr->num_trans > 0) && 2568 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0) 2569 { 2570 cmap_entries = (unsigned int)make_gray_file_colormap(display); 2571 data_encoding = P_FILE; 2572 } 2573 2574 else 2575 cmap_entries = (unsigned int)make_gray_colormap(display); 2576 2577 /* But if the input has alpha or transparency it must be removed 2578 */ 2579 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2580 png_ptr->num_trans > 0) 2581 { 2582 png_color_16 c; 2583 png_uint_32 gray = back_g; 2584 2585 /* We need to ensure that the application background exists in 2586 * the colormap and that completely transparent pixels map to 2587 * it. Achieve this simply by ensuring that the entry 2588 * selected for the background really is the background color. 2589 */ 2590 if (data_encoding == P_FILE) /* from the fixup above */ 2591 { 2592 /* The app supplied a gray which is in output_encoding, we 2593 * need to convert it to a value of the input (P_FILE) 2594 * encoding then set this palette entry to the required 2595 * output encoding. 2596 */ 2597 if (output_encoding == P_sRGB) 2598 gray = png_sRGB_table[gray]; /* now P_LINEAR */ 2599 2600 gray = PNG_DIV257(png_gamma_16bit_correct(gray, 2601 png_ptr->colorspace.gamma)); /* now P_FILE */ 2602 2603 /* And make sure the corresponding palette entry contains 2604 * exactly the required sRGB value. 2605 */ 2606 png_create_colormap_entry(display, gray, back_g, back_g, 2607 back_g, 0/*unused*/, output_encoding); 2608 } 2609 2610 else if (output_encoding == P_LINEAR) 2611 { 2612 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2613 2614 /* And make sure the corresponding palette entry matches. 2615 */ 2616 png_create_colormap_entry(display, gray, back_g, back_g, 2617 back_g, 0/*unused*/, P_LINEAR); 2618 } 2619 2620 /* The background passed to libpng, however, must be the 2621 * output (normally sRGB) value. 2622 */ 2623 c.index = 0; /*unused*/ 2624 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2625 2626 /* NOTE: the following is apparently a bug in libpng. Without 2627 * it the transparent color recognition in 2628 * png_set_background_fixed seems to go wrong. 2629 */ 2630 expand_tRNS = 1; 2631 png_set_background_fixed(png_ptr, &c, 2632 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2633 0/*gamma: not used*/); 2634 } 2635 2636 output_processing = PNG_CMAP_NONE; 2637 } 2638 } 2639 2640 else /* output is color */ 2641 { 2642 /* We could use png_quantize here so long as there is no transparent 2643 * color or alpha; png_quantize ignores alpha. Easier overall just 2644 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube. 2645 * Consequently we always want libpng to produce sRGB data. 2646 */ 2647 data_encoding = P_sRGB; 2648 2649 /* Is there any transparency or alpha? */ 2650 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2651 png_ptr->num_trans > 0) 2652 { 2653 /* Is there alpha in the output too? If so all four channels are 2654 * processed into a special RGB cube with alpha support. 2655 */ 2656 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0) 2657 { 2658 png_uint_32 r; 2659 2660 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries) 2661 png_error(png_ptr, "rgb+alpha color-map: too few entries"); 2662 2663 cmap_entries = (unsigned int)make_rgb_colormap(display); 2664 2665 /* Add a transparent entry. */ 2666 png_create_colormap_entry(display, cmap_entries, 255, 255, 2667 255, 0, P_sRGB); 2668 2669 /* This is stored as the background index for the processing 2670 * algorithm. 2671 */ 2672 background_index = cmap_entries++; 2673 2674 /* Add 27 r,g,b entries each with alpha 0.5. */ 2675 for (r=0; r<256; r = (r << 1) | 0x7f) 2676 { 2677 png_uint_32 g; 2678 2679 for (g=0; g<256; g = (g << 1) | 0x7f) 2680 { 2681 png_uint_32 b; 2682 2683 /* This generates components with the values 0, 127 and 2684 * 255 2685 */ 2686 for (b=0; b<256; b = (b << 1) | 0x7f) 2687 png_create_colormap_entry(display, cmap_entries++, 2688 r, g, b, 128, P_sRGB); 2689 } 2690 } 2691 2692 expand_tRNS = 1; 2693 output_processing = PNG_CMAP_RGB_ALPHA; 2694 } 2695 2696 else 2697 { 2698 /* Alpha/transparency must be removed. The background must 2699 * exist in the color map (achieved by setting adding it after 2700 * the 666 color-map). If the standard processing code will 2701 * pick up this entry automatically that's all that is 2702 * required; libpng can be called to do the background 2703 * processing. 2704 */ 2705 unsigned int sample_size = 2706 PNG_IMAGE_SAMPLE_SIZE(output_format); 2707 png_uint_32 r, g, b; /* sRGB background */ 2708 2709 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries) 2710 png_error(png_ptr, "rgb-alpha color-map: too few entries"); 2711 2712 cmap_entries = (unsigned int)make_rgb_colormap(display); 2713 2714 png_create_colormap_entry(display, cmap_entries, back_r, 2715 back_g, back_b, 0/*unused*/, output_encoding); 2716 2717 if (output_encoding == P_LINEAR) 2718 { 2719 r = PNG_sRGB_FROM_LINEAR(back_r * 255); 2720 g = PNG_sRGB_FROM_LINEAR(back_g * 255); 2721 b = PNG_sRGB_FROM_LINEAR(back_b * 255); 2722 } 2723 2724 else 2725 { 2726 r = back_r; 2727 g = back_g; 2728 b = back_g; 2729 } 2730 2731 /* Compare the newly-created color-map entry with the one the 2732 * PNG_CMAP_RGB algorithm will use. If the two entries don't 2733 * match, add the new one and set this as the background 2734 * index. 2735 */ 2736 if (memcmp((png_const_bytep)display->colormap + 2737 sample_size * cmap_entries, 2738 (png_const_bytep)display->colormap + 2739 sample_size * PNG_RGB_INDEX(r,g,b), 2740 sample_size) != 0) 2741 { 2742 /* The background color must be added. */ 2743 background_index = cmap_entries++; 2744 2745 /* Add 27 r,g,b entries each with created by composing with 2746 * the background at alpha 0.5. 2747 */ 2748 for (r=0; r<256; r = (r << 1) | 0x7f) 2749 { 2750 for (g=0; g<256; g = (g << 1) | 0x7f) 2751 { 2752 /* This generates components with the values 0, 127 2753 * and 255 2754 */ 2755 for (b=0; b<256; b = (b << 1) | 0x7f) 2756 png_create_colormap_entry(display, cmap_entries++, 2757 png_colormap_compose(display, r, P_sRGB, 128, 2758 back_r, output_encoding), 2759 png_colormap_compose(display, g, P_sRGB, 128, 2760 back_g, output_encoding), 2761 png_colormap_compose(display, b, P_sRGB, 128, 2762 back_b, output_encoding), 2763 0/*unused*/, output_encoding); 2764 } 2765 } 2766 2767 expand_tRNS = 1; 2768 output_processing = PNG_CMAP_RGB_ALPHA; 2769 } 2770 2771 else /* background color is in the standard color-map */ 2772 { 2773 png_color_16 c; 2774 2775 c.index = 0; /*unused*/ 2776 c.red = (png_uint_16)back_r; 2777 c.gray = c.green = (png_uint_16)back_g; 2778 c.blue = (png_uint_16)back_b; 2779 2780 png_set_background_fixed(png_ptr, &c, 2781 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2782 0/*gamma: not used*/); 2783 2784 output_processing = PNG_CMAP_RGB; 2785 } 2786 } 2787 } 2788 2789 else /* no alpha or transparency in the input */ 2790 { 2791 /* Alpha in the output is irrelevant, simply map the opaque input 2792 * pixels to the 6x6x6 color-map. 2793 */ 2794 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries) 2795 png_error(png_ptr, "rgb color-map: too few entries"); 2796 2797 cmap_entries = (unsigned int)make_rgb_colormap(display); 2798 output_processing = PNG_CMAP_RGB; 2799 } 2800 } 2801 break; 2802 2803 case PNG_COLOR_TYPE_PALETTE: 2804 /* It's already got a color-map. It may be necessary to eliminate the 2805 * tRNS entries though. 2806 */ 2807 { 2808 unsigned int num_trans = png_ptr->num_trans; 2809 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL; 2810 png_const_colorp colormap = png_ptr->palette; 2811 int do_background = trans != NULL && 2812 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0; 2813 unsigned int i; 2814 2815 /* Just in case: */ 2816 if (trans == NULL) 2817 num_trans = 0; 2818 2819 output_processing = PNG_CMAP_NONE; 2820 data_encoding = P_FILE; /* Don't change from color-map indices */ 2821 cmap_entries = (unsigned int)png_ptr->num_palette; 2822 if (cmap_entries > 256) 2823 cmap_entries = 256; 2824 2825 if (cmap_entries > (unsigned int)image->colormap_entries) 2826 png_error(png_ptr, "palette color-map: too few entries"); 2827 2828 for (i=0; i < cmap_entries; ++i) 2829 { 2830 if (do_background != 0 && i < num_trans && trans[i] < 255) 2831 { 2832 if (trans[i] == 0) 2833 png_create_colormap_entry(display, i, back_r, back_g, 2834 back_b, 0, output_encoding); 2835 2836 else 2837 { 2838 /* Must compose the PNG file color in the color-map entry 2839 * on the sRGB color in 'back'. 2840 */ 2841 png_create_colormap_entry(display, i, 2842 png_colormap_compose(display, colormap[i].red, 2843 P_FILE, trans[i], back_r, output_encoding), 2844 png_colormap_compose(display, colormap[i].green, 2845 P_FILE, trans[i], back_g, output_encoding), 2846 png_colormap_compose(display, colormap[i].blue, 2847 P_FILE, trans[i], back_b, output_encoding), 2848 output_encoding == P_LINEAR ? trans[i] * 257U : 2849 trans[i], 2850 output_encoding); 2851 } 2852 } 2853 2854 else 2855 png_create_colormap_entry(display, i, colormap[i].red, 2856 colormap[i].green, colormap[i].blue, 2857 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/); 2858 } 2859 2860 /* The PNG data may have indices packed in fewer than 8 bits, it 2861 * must be expanded if so. 2862 */ 2863 if (png_ptr->bit_depth < 8) 2864 png_set_packing(png_ptr); 2865 } 2866 break; 2867 2868 default: 2869 png_error(png_ptr, "invalid PNG color type"); 2870 /*NOT REACHED*/ 2871 } 2872 2873 /* Now deal with the output processing */ 2874 if (expand_tRNS != 0 && png_ptr->num_trans > 0 && 2875 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0) 2876 png_set_tRNS_to_alpha(png_ptr); 2877 2878 switch (data_encoding) 2879 { 2880 case P_sRGB: 2881 /* Change to 8-bit sRGB */ 2882 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB); 2883 /* FALLTHROUGH */ 2884 2885 case P_FILE: 2886 if (png_ptr->bit_depth > 8) 2887 png_set_scale_16(png_ptr); 2888 break; 2889 2890 #ifdef __GNUC__ 2891 default: 2892 png_error(png_ptr, "bad data option (internal error)"); 2893 #endif 2894 } 2895 2896 if (cmap_entries > 256 || cmap_entries > image->colormap_entries) 2897 png_error(png_ptr, "color map overflow (BAD internal error)"); 2898 2899 image->colormap_entries = cmap_entries; 2900 2901 /* Double check using the recorded background index */ 2902 switch (output_processing) 2903 { 2904 case PNG_CMAP_NONE: 2905 if (background_index != PNG_CMAP_NONE_BACKGROUND) 2906 goto bad_background; 2907 break; 2908 2909 case PNG_CMAP_GA: 2910 if (background_index != PNG_CMAP_GA_BACKGROUND) 2911 goto bad_background; 2912 break; 2913 2914 case PNG_CMAP_TRANS: 2915 if (background_index >= cmap_entries || 2916 background_index != PNG_CMAP_TRANS_BACKGROUND) 2917 goto bad_background; 2918 break; 2919 2920 case PNG_CMAP_RGB: 2921 if (background_index != PNG_CMAP_RGB_BACKGROUND) 2922 goto bad_background; 2923 break; 2924 2925 case PNG_CMAP_RGB_ALPHA: 2926 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND) 2927 goto bad_background; 2928 break; 2929 2930 default: 2931 png_error(png_ptr, "bad processing option (internal error)"); 2932 2933 bad_background: 2934 png_error(png_ptr, "bad background index (internal error)"); 2935 } 2936 2937 display->colormap_processing = (int)output_processing; 2938 2939 return 1/*ok*/; 2940 } 2941 2942 /* The final part of the color-map read called from png_image_finish_read. */ 2943 static int 2944 png_image_read_and_map(png_voidp argument) 2945 { 2946 png_image_read_control *display = png_voidcast(png_image_read_control*, 2947 argument); 2948 png_imagep image = display->image; 2949 png_structrp png_ptr = image->opaque->png_ptr; 2950 int passes; 2951 2952 /* Called when the libpng data must be transformed into the color-mapped 2953 * form. There is a local row buffer in display->local and this routine must 2954 * do the interlace handling. 2955 */ 2956 switch (png_ptr->interlaced) 2957 { 2958 case PNG_INTERLACE_NONE: 2959 passes = 1; 2960 break; 2961 2962 case PNG_INTERLACE_ADAM7: 2963 passes = PNG_INTERLACE_ADAM7_PASSES; 2964 break; 2965 2966 default: 2967 png_error(png_ptr, "unknown interlace type"); 2968 } 2969 2970 { 2971 png_uint_32 height = image->height; 2972 png_uint_32 width = image->width; 2973 int proc = display->colormap_processing; 2974 png_bytep first_row = png_voidcast(png_bytep, display->first_row); 2975 ptrdiff_t step_row = display->row_bytes; 2976 int pass; 2977 2978 for (pass = 0; pass < passes; ++pass) 2979 { 2980 unsigned int startx, stepx, stepy; 2981 png_uint_32 y; 2982 2983 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 2984 { 2985 /* The row may be empty for a short image: */ 2986 if (PNG_PASS_COLS(width, pass) == 0) 2987 continue; 2988 2989 startx = PNG_PASS_START_COL(pass); 2990 stepx = PNG_PASS_COL_OFFSET(pass); 2991 y = PNG_PASS_START_ROW(pass); 2992 stepy = PNG_PASS_ROW_OFFSET(pass); 2993 } 2994 2995 else 2996 { 2997 y = 0; 2998 startx = 0; 2999 stepx = stepy = 1; 3000 } 3001 3002 for (; y<height; y += stepy) 3003 { 3004 png_bytep inrow = png_voidcast(png_bytep, display->local_row); 3005 png_bytep outrow = first_row + y * step_row; 3006 png_const_bytep end_row = outrow + width; 3007 3008 /* Read read the libpng data into the temporary buffer. */ 3009 png_read_row(png_ptr, inrow, NULL); 3010 3011 /* Now process the row according to the processing option, note 3012 * that the caller verifies that the format of the libpng output 3013 * data is as required. 3014 */ 3015 outrow += startx; 3016 switch (proc) 3017 { 3018 case PNG_CMAP_GA: 3019 for (; outrow < end_row; outrow += stepx) 3020 { 3021 /* The data is always in the PNG order */ 3022 unsigned int gray = *inrow++; 3023 unsigned int alpha = *inrow++; 3024 unsigned int entry; 3025 3026 /* NOTE: this code is copied as a comment in 3027 * make_ga_colormap above. Please update the 3028 * comment if you change this code! 3029 */ 3030 if (alpha > 229) /* opaque */ 3031 { 3032 entry = (231 * gray + 128) >> 8; 3033 } 3034 else if (alpha < 26) /* transparent */ 3035 { 3036 entry = 231; 3037 } 3038 else /* partially opaque */ 3039 { 3040 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray); 3041 } 3042 3043 *outrow = (png_byte)entry; 3044 } 3045 break; 3046 3047 case PNG_CMAP_TRANS: 3048 for (; outrow < end_row; outrow += stepx) 3049 { 3050 png_byte gray = *inrow++; 3051 png_byte alpha = *inrow++; 3052 3053 if (alpha == 0) 3054 *outrow = PNG_CMAP_TRANS_BACKGROUND; 3055 3056 else if (gray != PNG_CMAP_TRANS_BACKGROUND) 3057 *outrow = gray; 3058 3059 else 3060 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1); 3061 } 3062 break; 3063 3064 case PNG_CMAP_RGB: 3065 for (; outrow < end_row; outrow += stepx) 3066 { 3067 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]); 3068 inrow += 3; 3069 } 3070 break; 3071 3072 case PNG_CMAP_RGB_ALPHA: 3073 for (; outrow < end_row; outrow += stepx) 3074 { 3075 unsigned int alpha = inrow[3]; 3076 3077 /* Because the alpha entries only hold alpha==0.5 values 3078 * split the processing at alpha==0.25 (64) and 0.75 3079 * (196). 3080 */ 3081 3082 if (alpha >= 196) 3083 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], 3084 inrow[2]); 3085 3086 else if (alpha < 64) 3087 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND; 3088 3089 else 3090 { 3091 /* Likewise there are three entries for each of r, g 3092 * and b. We could select the entry by popcount on 3093 * the top two bits on those architectures that 3094 * support it, this is what the code below does, 3095 * crudely. 3096 */ 3097 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1; 3098 3099 /* Here are how the values map: 3100 * 3101 * 0x00 .. 0x3f -> 0 3102 * 0x40 .. 0xbf -> 1 3103 * 0xc0 .. 0xff -> 2 3104 * 3105 * So, as above with the explicit alpha checks, the 3106 * breakpoints are at 64 and 196. 3107 */ 3108 if (inrow[0] & 0x80) back_i += 9; /* red */ 3109 if (inrow[0] & 0x40) back_i += 9; 3110 if (inrow[0] & 0x80) back_i += 3; /* green */ 3111 if (inrow[0] & 0x40) back_i += 3; 3112 if (inrow[0] & 0x80) back_i += 1; /* blue */ 3113 if (inrow[0] & 0x40) back_i += 1; 3114 3115 *outrow = (png_byte)back_i; 3116 } 3117 3118 inrow += 4; 3119 } 3120 break; 3121 3122 default: 3123 break; 3124 } 3125 } 3126 } 3127 } 3128 3129 return 1; 3130 } 3131 3132 static int 3133 png_image_read_colormapped(png_voidp argument) 3134 { 3135 png_image_read_control *display = png_voidcast(png_image_read_control*, 3136 argument); 3137 png_imagep image = display->image; 3138 png_controlp control = image->opaque; 3139 png_structrp png_ptr = control->png_ptr; 3140 png_inforp info_ptr = control->info_ptr; 3141 3142 int passes = 0; /* As a flag */ 3143 3144 PNG_SKIP_CHUNKS(png_ptr); 3145 3146 /* Update the 'info' structure and make sure the result is as required; first 3147 * make sure to turn on the interlace handling if it will be required 3148 * (because it can't be turned on *after* the call to png_read_update_info!) 3149 */ 3150 if (display->colormap_processing == PNG_CMAP_NONE) 3151 passes = png_set_interlace_handling(png_ptr); 3152 3153 png_read_update_info(png_ptr, info_ptr); 3154 3155 /* The expected output can be deduced from the colormap_processing option. */ 3156 switch (display->colormap_processing) 3157 { 3158 case PNG_CMAP_NONE: 3159 /* Output must be one channel and one byte per pixel, the output 3160 * encoding can be anything. 3161 */ 3162 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE || 3163 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) && 3164 info_ptr->bit_depth == 8) 3165 break; 3166 3167 goto bad_output; 3168 3169 case PNG_CMAP_TRANS: 3170 case PNG_CMAP_GA: 3171 /* Output must be two channels and the 'G' one must be sRGB, the latter 3172 * can be checked with an exact number because it should have been set 3173 * to this number above! 3174 */ 3175 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA && 3176 info_ptr->bit_depth == 8 && 3177 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3178 image->colormap_entries == 256) 3179 break; 3180 3181 goto bad_output; 3182 3183 case PNG_CMAP_RGB: 3184 /* Output must be 8-bit sRGB encoded RGB */ 3185 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB && 3186 info_ptr->bit_depth == 8 && 3187 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3188 image->colormap_entries == 216) 3189 break; 3190 3191 goto bad_output; 3192 3193 case PNG_CMAP_RGB_ALPHA: 3194 /* Output must be 8-bit sRGB encoded RGBA */ 3195 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA && 3196 info_ptr->bit_depth == 8 && 3197 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3198 image->colormap_entries == 244 /* 216 + 1 + 27 */) 3199 break; 3200 3201 goto bad_output; 3202 3203 default: 3204 bad_output: 3205 png_error(png_ptr, "bad color-map processing (internal error)"); 3206 } 3207 3208 /* Now read the rows. Do this here if it is possible to read directly into 3209 * the output buffer, otherwise allocate a local row buffer of the maximum 3210 * size libpng requires and call the relevant processing routine safely. 3211 */ 3212 { 3213 png_voidp first_row = display->buffer; 3214 ptrdiff_t row_bytes = display->row_stride; 3215 3216 /* The following expression is designed to work correctly whether it gives 3217 * a signed or an unsigned result. 3218 */ 3219 if (row_bytes < 0) 3220 { 3221 char *ptr = png_voidcast(char*, first_row); 3222 ptr += (image->height-1) * (-row_bytes); 3223 first_row = png_voidcast(png_voidp, ptr); 3224 } 3225 3226 display->first_row = first_row; 3227 display->row_bytes = row_bytes; 3228 } 3229 3230 if (passes == 0) 3231 { 3232 int result; 3233 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 3234 3235 display->local_row = row; 3236 result = png_safe_execute(image, png_image_read_and_map, display); 3237 display->local_row = NULL; 3238 png_free(png_ptr, row); 3239 3240 return result; 3241 } 3242 3243 else 3244 { 3245 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes; 3246 3247 while (--passes >= 0) 3248 { 3249 png_uint_32 y = image->height; 3250 png_bytep row = png_voidcast(png_bytep, display->first_row); 3251 3252 for (; y > 0; --y) 3253 { 3254 png_read_row(png_ptr, row, NULL); 3255 row += row_bytes; 3256 } 3257 } 3258 3259 return 1; 3260 } 3261 } 3262 3263 /* Just the row reading part of png_image_read. */ 3264 static int 3265 png_image_read_composite(png_voidp argument) 3266 { 3267 png_image_read_control *display = png_voidcast(png_image_read_control*, 3268 argument); 3269 png_imagep image = display->image; 3270 png_structrp png_ptr = image->opaque->png_ptr; 3271 int passes; 3272 3273 switch (png_ptr->interlaced) 3274 { 3275 case PNG_INTERLACE_NONE: 3276 passes = 1; 3277 break; 3278 3279 case PNG_INTERLACE_ADAM7: 3280 passes = PNG_INTERLACE_ADAM7_PASSES; 3281 break; 3282 3283 default: 3284 png_error(png_ptr, "unknown interlace type"); 3285 } 3286 3287 { 3288 png_uint_32 height = image->height; 3289 png_uint_32 width = image->width; 3290 ptrdiff_t step_row = display->row_bytes; 3291 unsigned int channels = 3292 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1; 3293 int pass; 3294 3295 for (pass = 0; pass < passes; ++pass) 3296 { 3297 unsigned int startx, stepx, stepy; 3298 png_uint_32 y; 3299 3300 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3301 { 3302 /* The row may be empty for a short image: */ 3303 if (PNG_PASS_COLS(width, pass) == 0) 3304 continue; 3305 3306 startx = PNG_PASS_START_COL(pass) * channels; 3307 stepx = PNG_PASS_COL_OFFSET(pass) * channels; 3308 y = PNG_PASS_START_ROW(pass); 3309 stepy = PNG_PASS_ROW_OFFSET(pass); 3310 } 3311 3312 else 3313 { 3314 y = 0; 3315 startx = 0; 3316 stepx = channels; 3317 stepy = 1; 3318 } 3319 3320 for (; y<height; y += stepy) 3321 { 3322 png_bytep inrow = png_voidcast(png_bytep, display->local_row); 3323 png_bytep outrow; 3324 png_const_bytep end_row; 3325 3326 /* Read the row, which is packed: */ 3327 png_read_row(png_ptr, inrow, NULL); 3328 3329 outrow = png_voidcast(png_bytep, display->first_row); 3330 outrow += y * step_row; 3331 end_row = outrow + width * channels; 3332 3333 /* Now do the composition on each pixel in this row. */ 3334 outrow += startx; 3335 for (; outrow < end_row; outrow += stepx) 3336 { 3337 png_byte alpha = inrow[channels]; 3338 3339 if (alpha > 0) /* else no change to the output */ 3340 { 3341 unsigned int c; 3342 3343 for (c=0; c<channels; ++c) 3344 { 3345 png_uint_32 component = inrow[c]; 3346 3347 if (alpha < 255) /* else just use component */ 3348 { 3349 /* This is PNG_OPTIMIZED_ALPHA, the component value 3350 * is a linear 8-bit value. Combine this with the 3351 * current outrow[c] value which is sRGB encoded. 3352 * Arithmetic here is 16-bits to preserve the output 3353 * values correctly. 3354 */ 3355 component *= 257*255; /* =65535 */ 3356 component += (255-alpha)*png_sRGB_table[outrow[c]]; 3357 3358 /* So 'component' is scaled by 255*65535 and is 3359 * therefore appropriate for the sRGB to linear 3360 * conversion table. 3361 */ 3362 component = PNG_sRGB_FROM_LINEAR(component); 3363 } 3364 3365 outrow[c] = (png_byte)component; 3366 } 3367 } 3368 3369 inrow += channels+1; /* components and alpha channel */ 3370 } 3371 } 3372 } 3373 } 3374 3375 return 1; 3376 } 3377 3378 /* The do_local_background case; called when all the following transforms are to 3379 * be done: 3380 * 3381 * PNG_RGB_TO_GRAY 3382 * PNG_COMPOSITE 3383 * PNG_GAMMA 3384 * 3385 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and 3386 * PNG_COMPOSITE code performs gamma correction, so we get double gamma 3387 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from 3388 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha 3389 * row and handles the removal or pre-multiplication of the alpha channel. 3390 */ 3391 static int 3392 png_image_read_background(png_voidp argument) 3393 { 3394 png_image_read_control *display = png_voidcast(png_image_read_control*, 3395 argument); 3396 png_imagep image = display->image; 3397 png_structrp png_ptr = image->opaque->png_ptr; 3398 png_inforp info_ptr = image->opaque->info_ptr; 3399 png_uint_32 height = image->height; 3400 png_uint_32 width = image->width; 3401 int pass, passes; 3402 3403 /* Double check the convoluted logic below. We expect to get here with 3404 * libpng doing rgb to gray and gamma correction but background processing 3405 * left to the png_image_read_background function. The rows libpng produce 3406 * might be 8 or 16-bit but should always have two channels; gray plus alpha. 3407 */ 3408 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0) 3409 png_error(png_ptr, "lost rgb to gray"); 3410 3411 if ((png_ptr->transformations & PNG_COMPOSE) != 0) 3412 png_error(png_ptr, "unexpected compose"); 3413 3414 if (png_get_channels(png_ptr, info_ptr) != 2) 3415 png_error(png_ptr, "lost/gained channels"); 3416 3417 /* Expect the 8-bit case to always remove the alpha channel */ 3418 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 && 3419 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0) 3420 png_error(png_ptr, "unexpected 8-bit transformation"); 3421 3422 switch (png_ptr->interlaced) 3423 { 3424 case PNG_INTERLACE_NONE: 3425 passes = 1; 3426 break; 3427 3428 case PNG_INTERLACE_ADAM7: 3429 passes = PNG_INTERLACE_ADAM7_PASSES; 3430 break; 3431 3432 default: 3433 png_error(png_ptr, "unknown interlace type"); 3434 } 3435 3436 /* Use direct access to info_ptr here because otherwise the simplified API 3437 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is 3438 * checking the value after libpng expansions, not the original value in the 3439 * PNG. 3440 */ 3441 switch (info_ptr->bit_depth) 3442 { 3443 case 8: 3444 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is 3445 * to be removed by composing on a background: either the row if 3446 * display->background is NULL or display->background->green if not. 3447 * Unlike the code above ALPHA_OPTIMIZED has *not* been done. 3448 */ 3449 { 3450 png_bytep first_row = png_voidcast(png_bytep, display->first_row); 3451 ptrdiff_t step_row = display->row_bytes; 3452 3453 for (pass = 0; pass < passes; ++pass) 3454 { 3455 unsigned int startx, stepx, stepy; 3456 png_uint_32 y; 3457 3458 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3459 { 3460 /* The row may be empty for a short image: */ 3461 if (PNG_PASS_COLS(width, pass) == 0) 3462 continue; 3463 3464 startx = PNG_PASS_START_COL(pass); 3465 stepx = PNG_PASS_COL_OFFSET(pass); 3466 y = PNG_PASS_START_ROW(pass); 3467 stepy = PNG_PASS_ROW_OFFSET(pass); 3468 } 3469 3470 else 3471 { 3472 y = 0; 3473 startx = 0; 3474 stepx = stepy = 1; 3475 } 3476 3477 if (display->background == NULL) 3478 { 3479 for (; y<height; y += stepy) 3480 { 3481 png_bytep inrow = png_voidcast(png_bytep, 3482 display->local_row); 3483 png_bytep outrow = first_row + y * step_row; 3484 png_const_bytep end_row = outrow + width; 3485 3486 /* Read the row, which is packed: */ 3487 png_read_row(png_ptr, inrow, NULL); 3488 3489 /* Now do the composition on each pixel in this row. */ 3490 outrow += startx; 3491 for (; outrow < end_row; outrow += stepx) 3492 { 3493 png_byte alpha = inrow[1]; 3494 3495 if (alpha > 0) /* else no change to the output */ 3496 { 3497 png_uint_32 component = inrow[0]; 3498 3499 if (alpha < 255) /* else just use component */ 3500 { 3501 /* Since PNG_OPTIMIZED_ALPHA was not set it is 3502 * necessary to invert the sRGB transfer 3503 * function and multiply the alpha out. 3504 */ 3505 component = png_sRGB_table[component] * alpha; 3506 component += png_sRGB_table[outrow[0]] * 3507 (255-alpha); 3508 component = PNG_sRGB_FROM_LINEAR(component); 3509 } 3510 3511 outrow[0] = (png_byte)component; 3512 } 3513 3514 inrow += 2; /* gray and alpha channel */ 3515 } 3516 } 3517 } 3518 3519 else /* constant background value */ 3520 { 3521 png_byte background8 = display->background->green; 3522 png_uint_16 background = png_sRGB_table[background8]; 3523 3524 for (; y<height; y += stepy) 3525 { 3526 png_bytep inrow = png_voidcast(png_bytep, 3527 display->local_row); 3528 png_bytep outrow = first_row + y * step_row; 3529 png_const_bytep end_row = outrow + width; 3530 3531 /* Read the row, which is packed: */ 3532 png_read_row(png_ptr, inrow, NULL); 3533 3534 /* Now do the composition on each pixel in this row. */ 3535 outrow += startx; 3536 for (; outrow < end_row; outrow += stepx) 3537 { 3538 png_byte alpha = inrow[1]; 3539 3540 if (alpha > 0) /* else use background */ 3541 { 3542 png_uint_32 component = inrow[0]; 3543 3544 if (alpha < 255) /* else just use component */ 3545 { 3546 component = png_sRGB_table[component] * alpha; 3547 component += background * (255-alpha); 3548 component = PNG_sRGB_FROM_LINEAR(component); 3549 } 3550 3551 outrow[0] = (png_byte)component; 3552 } 3553 3554 else 3555 outrow[0] = background8; 3556 3557 inrow += 2; /* gray and alpha channel */ 3558 } 3559 } 3560 } 3561 } 3562 } 3563 break; 3564 3565 case 16: 3566 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must 3567 * still be done and, maybe, the alpha channel removed. This code also 3568 * handles the alpha-first option. 3569 */ 3570 { 3571 png_uint_16p first_row = png_voidcast(png_uint_16p, 3572 display->first_row); 3573 /* The division by two is safe because the caller passed in a 3574 * stride which was multiplied by 2 (below) to get row_bytes. 3575 */ 3576 ptrdiff_t step_row = display->row_bytes / 2; 3577 unsigned int preserve_alpha = (image->format & 3578 PNG_FORMAT_FLAG_ALPHA) != 0; 3579 unsigned int outchannels = 1U+preserve_alpha; 3580 int swap_alpha = 0; 3581 3582 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED 3583 if (preserve_alpha != 0 && 3584 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0) 3585 swap_alpha = 1; 3586 # endif 3587 3588 for (pass = 0; pass < passes; ++pass) 3589 { 3590 unsigned int startx, stepx, stepy; 3591 png_uint_32 y; 3592 3593 /* The 'x' start and step are adjusted to output components here. 3594 */ 3595 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3596 { 3597 /* The row may be empty for a short image: */ 3598 if (PNG_PASS_COLS(width, pass) == 0) 3599 continue; 3600 3601 startx = PNG_PASS_START_COL(pass) * outchannels; 3602 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels; 3603 y = PNG_PASS_START_ROW(pass); 3604 stepy = PNG_PASS_ROW_OFFSET(pass); 3605 } 3606 3607 else 3608 { 3609 y = 0; 3610 startx = 0; 3611 stepx = outchannels; 3612 stepy = 1; 3613 } 3614 3615 for (; y<height; y += stepy) 3616 { 3617 png_const_uint_16p inrow; 3618 png_uint_16p outrow = first_row + y*step_row; 3619 png_uint_16p end_row = outrow + width * outchannels; 3620 3621 /* Read the row, which is packed: */ 3622 png_read_row(png_ptr, png_voidcast(png_bytep, 3623 display->local_row), NULL); 3624 inrow = png_voidcast(png_const_uint_16p, display->local_row); 3625 3626 /* Now do the pre-multiplication on each pixel in this row. 3627 */ 3628 outrow += startx; 3629 for (; outrow < end_row; outrow += stepx) 3630 { 3631 png_uint_32 component = inrow[0]; 3632 png_uint_16 alpha = inrow[1]; 3633 3634 if (alpha > 0) /* else 0 */ 3635 { 3636 if (alpha < 65535) /* else just use component */ 3637 { 3638 component *= alpha; 3639 component += 32767; 3640 component /= 65535; 3641 } 3642 } 3643 3644 else 3645 component = 0; 3646 3647 outrow[swap_alpha] = (png_uint_16)component; 3648 if (preserve_alpha != 0) 3649 outrow[1 ^ swap_alpha] = alpha; 3650 3651 inrow += 2; /* components and alpha channel */ 3652 } 3653 } 3654 } 3655 } 3656 break; 3657 3658 #ifdef __GNUC__ 3659 default: 3660 png_error(png_ptr, "unexpected bit depth"); 3661 #endif 3662 } 3663 3664 return 1; 3665 } 3666 3667 /* The guts of png_image_finish_read as a png_safe_execute callback. */ 3668 static int 3669 png_image_read_direct(png_voidp argument) 3670 { 3671 png_image_read_control *display = png_voidcast(png_image_read_control*, 3672 argument); 3673 png_imagep image = display->image; 3674 png_structrp png_ptr = image->opaque->png_ptr; 3675 png_inforp info_ptr = image->opaque->info_ptr; 3676 3677 png_uint_32 format = image->format; 3678 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0; 3679 int do_local_compose = 0; 3680 int do_local_background = 0; /* to avoid double gamma correction bug */ 3681 int passes = 0; 3682 3683 /* Add transforms to ensure the correct output format is produced then check 3684 * that the required implementation support is there. Always expand; always 3685 * need 8 bits minimum, no palette and expanded tRNS. 3686 */ 3687 png_set_expand(png_ptr); 3688 3689 /* Now check the format to see if it was modified. */ 3690 { 3691 png_uint_32 base_format = png_image_format(png_ptr) & 3692 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */; 3693 png_uint_32 change = format ^ base_format; 3694 png_fixed_point output_gamma; 3695 int mode; /* alpha mode */ 3696 3697 /* Do this first so that we have a record if rgb to gray is happening. */ 3698 if ((change & PNG_FORMAT_FLAG_COLOR) != 0) 3699 { 3700 /* gray<->color transformation required. */ 3701 if ((format & PNG_FORMAT_FLAG_COLOR) != 0) 3702 png_set_gray_to_rgb(png_ptr); 3703 3704 else 3705 { 3706 /* libpng can't do both rgb to gray and 3707 * background/pre-multiplication if there is also significant gamma 3708 * correction, because both operations require linear colors and 3709 * the code only supports one transform doing the gamma correction. 3710 * Handle this by doing the pre-multiplication or background 3711 * operation in this code, if necessary. 3712 * 3713 * TODO: fix this by rewriting pngrtran.c (!) 3714 * 3715 * For the moment (given that fixing this in pngrtran.c is an 3716 * enormous change) 'do_local_background' is used to indicate that 3717 * the problem exists. 3718 */ 3719 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0) 3720 do_local_background = 1/*maybe*/; 3721 3722 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, 3723 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT); 3724 } 3725 3726 change &= ~PNG_FORMAT_FLAG_COLOR; 3727 } 3728 3729 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise. 3730 */ 3731 { 3732 png_fixed_point input_gamma_default; 3733 3734 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 && 3735 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0) 3736 input_gamma_default = PNG_GAMMA_LINEAR; 3737 else 3738 input_gamma_default = PNG_DEFAULT_sRGB; 3739 3740 /* Call png_set_alpha_mode to set the default for the input gamma; the 3741 * output gamma is set by a second call below. 3742 */ 3743 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default); 3744 } 3745 3746 if (linear != 0) 3747 { 3748 /* If there *is* an alpha channel in the input it must be multiplied 3749 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG. 3750 */ 3751 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0) 3752 mode = PNG_ALPHA_STANDARD; /* associated alpha */ 3753 3754 else 3755 mode = PNG_ALPHA_PNG; 3756 3757 output_gamma = PNG_GAMMA_LINEAR; 3758 } 3759 3760 else 3761 { 3762 mode = PNG_ALPHA_PNG; 3763 output_gamma = PNG_DEFAULT_sRGB; 3764 } 3765 3766 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) 3767 { 3768 mode = PNG_ALPHA_OPTIMIZED; 3769 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA; 3770 } 3771 3772 /* If 'do_local_background' is set check for the presence of gamma 3773 * correction; this is part of the work-round for the libpng bug 3774 * described above. 3775 * 3776 * TODO: fix libpng and remove this. 3777 */ 3778 if (do_local_background != 0) 3779 { 3780 png_fixed_point gtest; 3781 3782 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for 3783 * gamma correction, the screen gamma hasn't been set on png_struct 3784 * yet; it's set below. png_struct::gamma, however, is set to the 3785 * final value. 3786 */ 3787 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma, 3788 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0) 3789 do_local_background = 0; 3790 3791 else if (mode == PNG_ALPHA_STANDARD) 3792 { 3793 do_local_background = 2/*required*/; 3794 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */ 3795 } 3796 3797 /* else leave as 1 for the checks below */ 3798 } 3799 3800 /* If the bit-depth changes then handle that here. */ 3801 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0) 3802 { 3803 if (linear != 0 /*16-bit output*/) 3804 png_set_expand_16(png_ptr); 3805 3806 else /* 8-bit output */ 3807 png_set_scale_16(png_ptr); 3808 3809 change &= ~PNG_FORMAT_FLAG_LINEAR; 3810 } 3811 3812 /* Now the background/alpha channel changes. */ 3813 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0) 3814 { 3815 /* Removing an alpha channel requires composition for the 8-bit 3816 * formats; for the 16-bit it is already done, above, by the 3817 * pre-multiplication and the channel just needs to be stripped. 3818 */ 3819 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0) 3820 { 3821 /* If RGB->gray is happening the alpha channel must be left and the 3822 * operation completed locally. 3823 * 3824 * TODO: fix libpng and remove this. 3825 */ 3826 if (do_local_background != 0) 3827 do_local_background = 2/*required*/; 3828 3829 /* 16-bit output: just remove the channel */ 3830 else if (linear != 0) /* compose on black (well, pre-multiply) */ 3831 png_set_strip_alpha(png_ptr); 3832 3833 /* 8-bit output: do an appropriate compose */ 3834 else if (display->background != NULL) 3835 { 3836 png_color_16 c; 3837 3838 c.index = 0; /*unused*/ 3839 c.red = display->background->red; 3840 c.green = display->background->green; 3841 c.blue = display->background->blue; 3842 c.gray = display->background->green; 3843 3844 /* This is always an 8-bit sRGB value, using the 'green' channel 3845 * for gray is much better than calculating the luminance here; 3846 * we can get off-by-one errors in that calculation relative to 3847 * the app expectations and that will show up in transparent 3848 * pixels. 3849 */ 3850 png_set_background_fixed(png_ptr, &c, 3851 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 3852 0/*gamma: not used*/); 3853 } 3854 3855 else /* compose on row: implemented below. */ 3856 { 3857 do_local_compose = 1; 3858 /* This leaves the alpha channel in the output, so it has to be 3859 * removed by the code below. Set the encoding to the 'OPTIMIZE' 3860 * one so the code only has to hack on the pixels that require 3861 * composition. 3862 */ 3863 mode = PNG_ALPHA_OPTIMIZED; 3864 } 3865 } 3866 3867 else /* output needs an alpha channel */ 3868 { 3869 /* This is tricky because it happens before the swap operation has 3870 * been accomplished; however, the swap does *not* swap the added 3871 * alpha channel (weird API), so it must be added in the correct 3872 * place. 3873 */ 3874 png_uint_32 filler; /* opaque filler */ 3875 int where; 3876 3877 if (linear != 0) 3878 filler = 65535; 3879 3880 else 3881 filler = 255; 3882 3883 #ifdef PNG_FORMAT_AFIRST_SUPPORTED 3884 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0) 3885 { 3886 where = PNG_FILLER_BEFORE; 3887 change &= ~PNG_FORMAT_FLAG_AFIRST; 3888 } 3889 3890 else 3891 #endif 3892 where = PNG_FILLER_AFTER; 3893 3894 png_set_add_alpha(png_ptr, filler, where); 3895 } 3896 3897 /* This stops the (irrelevant) call to swap_alpha below. */ 3898 change &= ~PNG_FORMAT_FLAG_ALPHA; 3899 } 3900 3901 /* Now set the alpha mode correctly; this is always done, even if there is 3902 * no alpha channel in either the input or the output because it correctly 3903 * sets the output gamma. 3904 */ 3905 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma); 3906 3907 # ifdef PNG_FORMAT_BGR_SUPPORTED 3908 if ((change & PNG_FORMAT_FLAG_BGR) != 0) 3909 { 3910 /* Check only the output format; PNG is never BGR; don't do this if 3911 * the output is gray, but fix up the 'format' value in that case. 3912 */ 3913 if ((format & PNG_FORMAT_FLAG_COLOR) != 0) 3914 png_set_bgr(png_ptr); 3915 3916 else 3917 format &= ~PNG_FORMAT_FLAG_BGR; 3918 3919 change &= ~PNG_FORMAT_FLAG_BGR; 3920 } 3921 # endif 3922 3923 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 3924 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0) 3925 { 3926 /* Only relevant if there is an alpha channel - it's particularly 3927 * important to handle this correctly because do_local_compose may 3928 * be set above and then libpng will keep the alpha channel for this 3929 * code to remove. 3930 */ 3931 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0) 3932 { 3933 /* Disable this if doing a local background, 3934 * TODO: remove this when local background is no longer required. 3935 */ 3936 if (do_local_background != 2) 3937 png_set_swap_alpha(png_ptr); 3938 } 3939 3940 else 3941 format &= ~PNG_FORMAT_FLAG_AFIRST; 3942 3943 change &= ~PNG_FORMAT_FLAG_AFIRST; 3944 } 3945 # endif 3946 3947 /* If the *output* is 16-bit then we need to check for a byte-swap on this 3948 * architecture. 3949 */ 3950 if (linear != 0) 3951 { 3952 png_uint_16 le = 0x0001; 3953 3954 if ((*(png_const_bytep) & le) != 0) 3955 png_set_swap(png_ptr); 3956 } 3957 3958 /* If change is not now 0 some transformation is missing - error out. */ 3959 if (change != 0) 3960 png_error(png_ptr, "png_read_image: unsupported transformation"); 3961 } 3962 3963 PNG_SKIP_CHUNKS(png_ptr); 3964 3965 /* Update the 'info' structure and make sure the result is as required; first 3966 * make sure to turn on the interlace handling if it will be required 3967 * (because it can't be turned on *after* the call to png_read_update_info!) 3968 * 3969 * TODO: remove the do_local_background fixup below. 3970 */ 3971 if (do_local_compose == 0 && do_local_background != 2) 3972 passes = png_set_interlace_handling(png_ptr); 3973 3974 png_read_update_info(png_ptr, info_ptr); 3975 3976 { 3977 png_uint_32 info_format = 0; 3978 3979 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0) 3980 info_format |= PNG_FORMAT_FLAG_COLOR; 3981 3982 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0) 3983 { 3984 /* do_local_compose removes this channel below. */ 3985 if (do_local_compose == 0) 3986 { 3987 /* do_local_background does the same if required. */ 3988 if (do_local_background != 2 || 3989 (format & PNG_FORMAT_FLAG_ALPHA) != 0) 3990 info_format |= PNG_FORMAT_FLAG_ALPHA; 3991 } 3992 } 3993 3994 else if (do_local_compose != 0) /* internal error */ 3995 png_error(png_ptr, "png_image_read: alpha channel lost"); 3996 3997 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) { 3998 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA; 3999 } 4000 4001 if (info_ptr->bit_depth == 16) 4002 info_format |= PNG_FORMAT_FLAG_LINEAR; 4003 4004 #ifdef PNG_FORMAT_BGR_SUPPORTED 4005 if ((png_ptr->transformations & PNG_BGR) != 0) 4006 info_format |= PNG_FORMAT_FLAG_BGR; 4007 #endif 4008 4009 #ifdef PNG_FORMAT_AFIRST_SUPPORTED 4010 if (do_local_background == 2) 4011 { 4012 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0) 4013 info_format |= PNG_FORMAT_FLAG_AFIRST; 4014 } 4015 4016 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 || 4017 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 && 4018 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0)) 4019 { 4020 if (do_local_background == 2) 4021 png_error(png_ptr, "unexpected alpha swap transformation"); 4022 4023 info_format |= PNG_FORMAT_FLAG_AFIRST; 4024 } 4025 # endif 4026 4027 /* This is actually an internal error. */ 4028 if (info_format != format) 4029 png_error(png_ptr, "png_read_image: invalid transformations"); 4030 } 4031 4032 /* Now read the rows. If do_local_compose is set then it is necessary to use 4033 * a local row buffer. The output will be GA, RGBA or BGRA and must be 4034 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the 4035 * display acts as a flag. 4036 */ 4037 { 4038 png_voidp first_row = display->buffer; 4039 ptrdiff_t row_bytes = display->row_stride; 4040 4041 if (linear != 0) 4042 row_bytes *= 2; 4043 4044 /* The following expression is designed to work correctly whether it gives 4045 * a signed or an unsigned result. 4046 */ 4047 if (row_bytes < 0) 4048 { 4049 char *ptr = png_voidcast(char*, first_row); 4050 ptr += (image->height-1) * (-row_bytes); 4051 first_row = png_voidcast(png_voidp, ptr); 4052 } 4053 4054 display->first_row = first_row; 4055 display->row_bytes = row_bytes; 4056 } 4057 4058 if (do_local_compose != 0) 4059 { 4060 int result; 4061 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 4062 4063 display->local_row = row; 4064 result = png_safe_execute(image, png_image_read_composite, display); 4065 display->local_row = NULL; 4066 png_free(png_ptr, row); 4067 4068 return result; 4069 } 4070 4071 else if (do_local_background == 2) 4072 { 4073 int result; 4074 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 4075 4076 display->local_row = row; 4077 result = png_safe_execute(image, png_image_read_background, display); 4078 display->local_row = NULL; 4079 png_free(png_ptr, row); 4080 4081 return result; 4082 } 4083 4084 else 4085 { 4086 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes; 4087 4088 while (--passes >= 0) 4089 { 4090 png_uint_32 y = image->height; 4091 png_bytep row = png_voidcast(png_bytep, display->first_row); 4092 4093 for (; y > 0; --y) 4094 { 4095 png_read_row(png_ptr, row, NULL); 4096 row += row_bytes; 4097 } 4098 } 4099 4100 return 1; 4101 } 4102 } 4103 4104 int PNGAPI 4105 png_image_finish_read(png_imagep image, png_const_colorp background, 4106 void *buffer, png_int_32 row_stride, void *colormap) 4107 { 4108 if (image != NULL && image->version == PNG_IMAGE_VERSION) 4109 { 4110 /* Check for row_stride overflow. This check is not performed on the 4111 * original PNG format because it may not occur in the output PNG format 4112 * and libpng deals with the issues of reading the original. 4113 */ 4114 unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format); 4115 4116 /* The following checks just the 'row_stride' calculation to ensure it 4117 * fits in a signed 32-bit value. Because channels/components can be 4118 * either 1 or 2 bytes in size the length of a row can still overflow 32 4119 * bits; this is just to verify that the 'row_stride' argument can be 4120 * represented. 4121 */ 4122 if (image->width <= 0x7fffffffU/channels) /* no overflow */ 4123 { 4124 png_uint_32 check; 4125 png_uint_32 png_row_stride = image->width * channels; 4126 4127 if (row_stride == 0) 4128 row_stride = (png_int_32)/*SAFE*/png_row_stride; 4129 4130 if (row_stride < 0) 4131 check = (png_uint_32)(-row_stride); 4132 4133 else 4134 check = (png_uint_32)row_stride; 4135 4136 /* This verifies 'check', the absolute value of the actual stride 4137 * passed in and detects overflow in the application calculation (i.e. 4138 * if the app did actually pass in a non-zero 'row_stride'. 4139 */ 4140 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride) 4141 { 4142 /* Now check for overflow of the image buffer calculation; this 4143 * limits the whole image size to 32 bits for API compatibility with 4144 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro. 4145 * 4146 * The PNG_IMAGE_BUFFER_SIZE macro is: 4147 * 4148 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride)) 4149 * 4150 * And the component size is always 1 or 2, so make sure that the 4151 * number of *bytes* that the application is saying are available 4152 * does actually fit into a 32-bit number. 4153 * 4154 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE 4155 * will be changed to use png_alloc_size_t; bigger images can be 4156 * accommodated on 64-bit systems. 4157 */ 4158 if (image->height <= 4159 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check) 4160 { 4161 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 || 4162 (image->colormap_entries > 0 && colormap != NULL)) 4163 { 4164 int result; 4165 png_image_read_control display; 4166 4167 memset(&display, 0, (sizeof display)); 4168 display.image = image; 4169 display.buffer = buffer; 4170 display.row_stride = row_stride; 4171 display.colormap = colormap; 4172 display.background = background; 4173 display.local_row = NULL; 4174 4175 /* Choose the correct 'end' routine; for the color-map case 4176 * all the setup has already been done. 4177 */ 4178 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0) 4179 result = 4180 png_safe_execute(image, 4181 png_image_read_colormap, &display) && 4182 png_safe_execute(image, 4183 png_image_read_colormapped, &display); 4184 4185 else 4186 result = 4187 png_safe_execute(image, 4188 png_image_read_direct, &display); 4189 4190 png_image_free(image); 4191 return result; 4192 } 4193 4194 else 4195 return png_image_error(image, 4196 "png_image_finish_read[color-map]: no color-map"); 4197 } 4198 4199 else 4200 return png_image_error(image, 4201 "png_image_finish_read: image too large"); 4202 } 4203 4204 else 4205 return png_image_error(image, 4206 "png_image_finish_read: invalid argument"); 4207 } 4208 4209 else 4210 return png_image_error(image, 4211 "png_image_finish_read: row_stride too large"); 4212 } 4213 4214 else if (image != NULL) 4215 return png_image_error(image, 4216 "png_image_finish_read: damaged PNG_IMAGE_VERSION"); 4217 4218 return 0; 4219 } 4220 4221 #endif /* SIMPLIFIED_READ */ 4222 #endif /* READ */ 4223