1 /* 2 * rdjpgcom.c 3 * 4 * Copyright (C) 1994-1997, Thomas G. Lane. 5 * Modified 2009 by Bill Allombert, Guido Vollbeding. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains a very simple stand-alone application that displays 10 * the text in COM (comment) markers in a JFIF file. 11 * This may be useful as an example of the minimum logic needed to parse 12 * JPEG markers. 13 */ 14 15 #define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */ 16 #include "jinclude.h" /* get auto-config symbols, <stdio.h> */ 17 18 #ifdef HAVE_LOCALE_H 19 #include <locale.h> /* Bill Allombert: use locale for isprint */ 20 #endif 21 #include <ctype.h> /* to declare isupper(), tolower() */ 22 #ifdef USE_SETMODE 23 #include <fcntl.h> /* to declare setmode()'s parameter macros */ 24 /* If you have setmode() but not <io.h>, just delete this line: */ 25 #include <io.h> /* to declare setmode() */ 26 #endif 27 28 #ifdef USE_CCOMMAND /* command-line reader for Macintosh */ 29 #ifdef __MWERKS__ 30 #include <SIOUX.h> /* Metrowerks needs this */ 31 #include <console.h> /* ... and this */ 32 #endif 33 #ifdef THINK_C 34 #include <console.h> /* Think declares it here */ 35 #endif 36 #endif 37 38 #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */ 39 #define READ_BINARY "r" 40 #else 41 #ifdef VMS /* VMS is very nonstandard */ 42 #define READ_BINARY "rb", "ctx=stm" 43 #else /* standard ANSI-compliant case */ 44 #define READ_BINARY "rb" 45 #endif 46 #endif 47 48 #ifndef EXIT_FAILURE /* define exit() codes if not provided */ 49 #define EXIT_FAILURE 1 50 #endif 51 #ifndef EXIT_SUCCESS 52 #ifdef VMS 53 #define EXIT_SUCCESS 1 /* VMS is very nonstandard */ 54 #else 55 #define EXIT_SUCCESS 0 56 #endif 57 #endif 58 59 60 /* 61 * These macros are used to read the input file. 62 * To reuse this code in another application, you might need to change these. 63 */ 64 65 static FILE * infile; /* input JPEG file */ 66 67 /* Return next input byte, or EOF if no more */ 68 #define NEXTBYTE() getc(infile) 69 70 71 /* Error exit handler */ 72 #define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE)) 73 74 75 /* Read one byte, testing for EOF */ 76 static int 77 read_1_byte (void) 78 { 79 int c; 80 81 c = NEXTBYTE(); 82 if (c == EOF) 83 ERREXIT("Premature EOF in JPEG file"); 84 return c; 85 } 86 87 /* Read 2 bytes, convert to unsigned int */ 88 /* All 2-byte quantities in JPEG markers are MSB first */ 89 static unsigned int 90 read_2_bytes (void) 91 { 92 int c1, c2; 93 94 c1 = NEXTBYTE(); 95 if (c1 == EOF) 96 ERREXIT("Premature EOF in JPEG file"); 97 c2 = NEXTBYTE(); 98 if (c2 == EOF) 99 ERREXIT("Premature EOF in JPEG file"); 100 return (((unsigned int) c1) << 8) + ((unsigned int) c2); 101 } 102 103 104 /* 105 * JPEG markers consist of one or more 0xFF bytes, followed by a marker 106 * code byte (which is not an FF). Here are the marker codes of interest 107 * in this program. (See jdmarker.c for a more complete list.) 108 */ 109 110 #define M_SOF0 0xC0 /* Start Of Frame N */ 111 #define M_SOF1 0xC1 /* N indicates which compression process */ 112 #define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */ 113 #define M_SOF3 0xC3 114 #define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */ 115 #define M_SOF6 0xC6 116 #define M_SOF7 0xC7 117 #define M_SOF9 0xC9 118 #define M_SOF10 0xCA 119 #define M_SOF11 0xCB 120 #define M_SOF13 0xCD 121 #define M_SOF14 0xCE 122 #define M_SOF15 0xCF 123 #define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */ 124 #define M_EOI 0xD9 /* End Of Image (end of datastream) */ 125 #define M_SOS 0xDA /* Start Of Scan (begins compressed data) */ 126 #define M_APP0 0xE0 /* Application-specific marker, type N */ 127 #define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */ 128 #define M_COM 0xFE /* COMment */ 129 130 131 /* 132 * Find the next JPEG marker and return its marker code. 133 * We expect at least one FF byte, possibly more if the compressor used FFs 134 * to pad the file. 135 * There could also be non-FF garbage between markers. The treatment of such 136 * garbage is unspecified; we choose to skip over it but emit a warning msg. 137 * NB: this routine must not be used after seeing SOS marker, since it will 138 * not deal correctly with FF/00 sequences in the compressed image data... 139 */ 140 141 static int 142 next_marker (void) 143 { 144 int c; 145 int discarded_bytes = 0; 146 147 /* Find 0xFF byte; count and skip any non-FFs. */ 148 c = read_1_byte(); 149 while (c != 0xFF) { 150 discarded_bytes++; 151 c = read_1_byte(); 152 } 153 /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs 154 * are legal as pad bytes, so don't count them in discarded_bytes. 155 */ 156 do { 157 c = read_1_byte(); 158 } while (c == 0xFF); 159 160 if (discarded_bytes != 0) { 161 fprintf(stderr, "Warning: garbage data found in JPEG file\n"); 162 } 163 164 return c; 165 } 166 167 168 /* 169 * Read the initial marker, which should be SOI. 170 * For a JFIF file, the first two bytes of the file should be literally 171 * 0xFF M_SOI. To be more general, we could use next_marker, but if the 172 * input file weren't actually JPEG at all, next_marker might read the whole 173 * file and then return a misleading error message... 174 */ 175 176 static int 177 first_marker (void) 178 { 179 int c1, c2; 180 181 c1 = NEXTBYTE(); 182 c2 = NEXTBYTE(); 183 if (c1 != 0xFF || c2 != M_SOI) 184 ERREXIT("Not a JPEG file"); 185 return c2; 186 } 187 188 189 /* 190 * Most types of marker are followed by a variable-length parameter segment. 191 * This routine skips over the parameters for any marker we don't otherwise 192 * want to process. 193 * Note that we MUST skip the parameter segment explicitly in order not to 194 * be fooled by 0xFF bytes that might appear within the parameter segment; 195 * such bytes do NOT introduce new markers. 196 */ 197 198 static void 199 skip_variable (void) 200 /* Skip over an unknown or uninteresting variable-length marker */ 201 { 202 unsigned int length; 203 204 /* Get the marker parameter length count */ 205 length = read_2_bytes(); 206 /* Length includes itself, so must be at least 2 */ 207 if (length < 2) 208 ERREXIT("Erroneous JPEG marker length"); 209 length -= 2; 210 /* Skip over the remaining bytes */ 211 while (length > 0) { 212 (void) read_1_byte(); 213 length--; 214 } 215 } 216 217 218 /* 219 * Process a COM marker. 220 * We want to print out the marker contents as legible text; 221 * we must guard against non-text junk and varying newline representations. 222 */ 223 224 static void 225 process_COM (int raw) 226 { 227 unsigned int length; 228 int ch; 229 int lastch = 0; 230 231 /* Bill Allombert: set locale properly for isprint */ 232 #ifdef HAVE_LOCALE_H 233 setlocale(LC_CTYPE, ""); 234 #endif 235 236 /* Get the marker parameter length count */ 237 length = read_2_bytes(); 238 /* Length includes itself, so must be at least 2 */ 239 if (length < 2) 240 ERREXIT("Erroneous JPEG marker length"); 241 length -= 2; 242 243 while (length > 0) { 244 ch = read_1_byte(); 245 if (raw) { 246 putc(ch, stdout); 247 /* Emit the character in a readable form. 248 * Nonprintables are converted to \nnn form, 249 * while \ is converted to \\. 250 * Newlines in CR, CR/LF, or LF form will be printed as one newline. 251 */ 252 } else if (ch == '\r') { 253 printf("\n"); 254 } else if (ch == '\n') { 255 if (lastch != '\r') 256 printf("\n"); 257 } else if (ch == '\\') { 258 printf("\\\\"); 259 } else if (isprint(ch)) { 260 putc(ch, stdout); 261 } else { 262 printf("\\%03o", ch); 263 } 264 lastch = ch; 265 length--; 266 } 267 printf("\n"); 268 269 /* Bill Allombert: revert to C locale */ 270 #ifdef HAVE_LOCALE_H 271 setlocale(LC_CTYPE, "C"); 272 #endif 273 } 274 275 276 /* 277 * Process a SOFn marker. 278 * This code is only needed if you want to know the image dimensions... 279 */ 280 281 static void 282 process_SOFn (int marker) 283 { 284 unsigned int length; 285 unsigned int image_height, image_width; 286 int data_precision, num_components; 287 const char * process; 288 int ci; 289 290 length = read_2_bytes(); /* usual parameter length count */ 291 292 data_precision = read_1_byte(); 293 image_height = read_2_bytes(); 294 image_width = read_2_bytes(); 295 num_components = read_1_byte(); 296 297 switch (marker) { 298 case M_SOF0: process = "Baseline"; break; 299 case M_SOF1: process = "Extended sequential"; break; 300 case M_SOF2: process = "Progressive"; break; 301 case M_SOF3: process = "Lossless"; break; 302 case M_SOF5: process = "Differential sequential"; break; 303 case M_SOF6: process = "Differential progressive"; break; 304 case M_SOF7: process = "Differential lossless"; break; 305 case M_SOF9: process = "Extended sequential, arithmetic coding"; break; 306 case M_SOF10: process = "Progressive, arithmetic coding"; break; 307 case M_SOF11: process = "Lossless, arithmetic coding"; break; 308 case M_SOF13: process = "Differential sequential, arithmetic coding"; break; 309 case M_SOF14: process = "Differential progressive, arithmetic coding"; break; 310 case M_SOF15: process = "Differential lossless, arithmetic coding"; break; 311 default: process = "Unknown"; break; 312 } 313 314 printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n", 315 image_width, image_height, num_components, data_precision); 316 printf("JPEG process: %s\n", process); 317 318 if (length != (unsigned int) (8 + num_components * 3)) 319 ERREXIT("Bogus SOF marker length"); 320 321 for (ci = 0; ci < num_components; ci++) { 322 (void) read_1_byte(); /* Component ID code */ 323 (void) read_1_byte(); /* H, V sampling factors */ 324 (void) read_1_byte(); /* Quantization table number */ 325 } 326 } 327 328 329 /* 330 * Parse the marker stream until SOS or EOI is seen; 331 * display any COM markers. 332 * While the companion program wrjpgcom will always insert COM markers before 333 * SOFn, other implementations might not, so we scan to SOS before stopping. 334 * If we were only interested in the image dimensions, we would stop at SOFn. 335 * (Conversely, if we only cared about COM markers, there would be no need 336 * for special code to handle SOFn; we could treat it like other markers.) 337 */ 338 339 static int 340 scan_JPEG_header (int verbose, int raw) 341 { 342 int marker; 343 344 /* Expect SOI at start of file */ 345 if (first_marker() != M_SOI) 346 ERREXIT("Expected SOI marker first"); 347 348 /* Scan miscellaneous markers until we reach SOS. */ 349 for (;;) { 350 marker = next_marker(); 351 switch (marker) { 352 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be, 353 * treated as SOFn. C4 in particular is actually DHT. 354 */ 355 case M_SOF0: /* Baseline */ 356 case M_SOF1: /* Extended sequential, Huffman */ 357 case M_SOF2: /* Progressive, Huffman */ 358 case M_SOF3: /* Lossless, Huffman */ 359 case M_SOF5: /* Differential sequential, Huffman */ 360 case M_SOF6: /* Differential progressive, Huffman */ 361 case M_SOF7: /* Differential lossless, Huffman */ 362 case M_SOF9: /* Extended sequential, arithmetic */ 363 case M_SOF10: /* Progressive, arithmetic */ 364 case M_SOF11: /* Lossless, arithmetic */ 365 case M_SOF13: /* Differential sequential, arithmetic */ 366 case M_SOF14: /* Differential progressive, arithmetic */ 367 case M_SOF15: /* Differential lossless, arithmetic */ 368 if (verbose) 369 process_SOFn(marker); 370 else 371 skip_variable(); 372 break; 373 374 case M_SOS: /* stop before hitting compressed data */ 375 return marker; 376 377 case M_EOI: /* in case it's a tables-only JPEG stream */ 378 return marker; 379 380 case M_COM: 381 process_COM(raw); 382 break; 383 384 case M_APP12: 385 /* Some digital camera makers put useful textual information into 386 * APP12 markers, so we print those out too when in -verbose mode. 387 */ 388 if (verbose) { 389 printf("APP12 contains:\n"); 390 process_COM(raw); 391 } else 392 skip_variable(); 393 break; 394 395 default: /* Anything else just gets skipped */ 396 skip_variable(); /* we assume it has a parameter count... */ 397 break; 398 } 399 } /* end loop */ 400 } 401 402 403 /* Command line parsing code */ 404 405 static const char * progname; /* program name for error messages */ 406 407 408 static void 409 usage (void) 410 /* complain about bad command line */ 411 { 412 fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n"); 413 414 fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname); 415 416 fprintf(stderr, "Switches (names may be abbreviated):\n"); 417 fprintf(stderr, " -raw Display non-printable characters in comments (unsafe)\n"); 418 fprintf(stderr, " -verbose Also display dimensions of JPEG image\n"); 419 420 exit(EXIT_FAILURE); 421 } 422 423 424 static int 425 keymatch (char * arg, const char * keyword, int minchars) 426 /* Case-insensitive matching of (possibly abbreviated) keyword switches. */ 427 /* keyword is the constant keyword (must be lower case already), */ 428 /* minchars is length of minimum legal abbreviation. */ 429 { 430 register int ca, ck; 431 register int nmatched = 0; 432 433 while ((ca = *arg++) != '\0') { 434 if ((ck = *keyword++) == '\0') 435 return 0; /* arg longer than keyword, no good */ 436 if (isupper(ca)) /* force arg to lcase (assume ck is already) */ 437 ca = tolower(ca); 438 if (ca != ck) 439 return 0; /* no good */ 440 nmatched++; /* count matched characters */ 441 } 442 /* reached end of argument; fail if it's too short for unique abbrev */ 443 if (nmatched < minchars) 444 return 0; 445 return 1; /* A-OK */ 446 } 447 448 449 /* 450 * The main program. 451 */ 452 453 int 454 main (int argc, char **argv) 455 { 456 int argn; 457 char * arg; 458 int verbose = 0, raw = 0; 459 460 /* On Mac, fetch a command line. */ 461 #ifdef USE_CCOMMAND 462 argc = ccommand(&argv); 463 #endif 464 465 progname = argv[0]; 466 if (progname == NULL || progname[0] == 0) 467 progname = "rdjpgcom"; /* in case C library doesn't provide it */ 468 469 /* Parse switches, if any */ 470 for (argn = 1; argn < argc; argn++) { 471 arg = argv[argn]; 472 if (arg[0] != '-') 473 break; /* not switch, must be file name */ 474 arg++; /* advance over '-' */ 475 if (keymatch(arg, "verbose", 1)) { 476 verbose++; 477 } else if (keymatch(arg, "raw", 1)) { 478 raw = 1; 479 } else 480 usage(); 481 } 482 483 /* Open the input file. */ 484 /* Unix style: expect zero or one file name */ 485 if (argn < argc-1) { 486 fprintf(stderr, "%s: only one input file\n", progname); 487 usage(); 488 } 489 if (argn < argc) { 490 if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) { 491 fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]); 492 exit(EXIT_FAILURE); 493 } 494 } else { 495 /* default input file is stdin */ 496 #ifdef USE_SETMODE /* need to hack file mode? */ 497 setmode(fileno(stdin), O_BINARY); 498 #endif 499 #ifdef USE_FDOPEN /* need to re-open in binary mode? */ 500 if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) { 501 fprintf(stderr, "%s: can't open stdin\n", progname); 502 exit(EXIT_FAILURE); 503 } 504 #else 505 infile = stdin; 506 #endif 507 } 508 509 /* Scan the JPEG headers. */ 510 (void) scan_JPEG_header(verbose, raw); 511 512 /* All done. */ 513 exit(EXIT_SUCCESS); 514 return 0; /* suppress no-return-value warnings */ 515 } 516