1 /* 2 * jdct.h 3 * 4 * Copyright (C) 1994-1996, Thomas G. Lane. 5 * Modified 2002-2017 by 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 include file contains common declarations for the forward and 10 * inverse DCT modules. These declarations are private to the DCT managers 11 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms. 12 * The individual DCT algorithms are kept in separate files to ease 13 * machine-dependent tuning (e.g., assembly coding). 14 */ 15 16 17 /* 18 * A forward DCT routine is given a pointer to an input sample array and 19 * a pointer to a work area of type DCTELEM[]; the DCT is to be performed 20 * in-place in that buffer. Type DCTELEM is int for 8-bit samples, INT32 21 * for 12-bit samples. (NOTE: Floating-point DCT implementations use an 22 * array of type FAST_FLOAT, instead.) 23 * The input data is to be fetched from the sample array starting at a 24 * specified column. (Any row offset needed will be applied to the array 25 * pointer before it is passed to the FDCT code.) 26 * Note that the number of samples fetched by the FDCT routine is 27 * DCT_h_scaled_size * DCT_v_scaled_size. 28 * The DCT outputs are returned scaled up by a factor of 8; they therefore 29 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This 30 * convention improves accuracy in integer implementations and saves some 31 * work in floating-point ones. 32 * Quantization of the output coefficients is done by jcdctmgr.c. 33 */ 34 35 #if BITS_IN_JSAMPLE == 8 36 typedef int DCTELEM; /* 16 or 32 bits is fine */ 37 #else 38 typedef INT32 DCTELEM; /* must have 32 bits */ 39 #endif 40 41 typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data, 42 JSAMPARRAY sample_data, 43 JDIMENSION start_col)); 44 typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data, 45 JSAMPARRAY sample_data, 46 JDIMENSION start_col)); 47 48 49 /* 50 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer 51 * to an output sample array. The routine must dequantize the input data as 52 * well as perform the IDCT; for dequantization, it uses the multiplier table 53 * pointed to by compptr->dct_table. The output data is to be placed into the 54 * sample array starting at a specified column. (Any row offset needed will 55 * be applied to the array pointer before it is passed to the IDCT code.) 56 * Note that the number of samples emitted by the IDCT routine is 57 * DCT_h_scaled_size * DCT_v_scaled_size. 58 */ 59 60 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */ 61 62 /* 63 * Each IDCT routine has its own ideas about the best dct_table element type. 64 */ 65 66 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ 67 #if BITS_IN_JSAMPLE == 8 68 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ 69 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */ 70 #else 71 typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ 72 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */ 73 #endif 74 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ 75 76 77 /* 78 * Each IDCT routine is responsible for range-limiting its results and 79 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could 80 * be quite far out of range if the input data is corrupt, so a bulletproof 81 * range-limiting step is required. We use a mask-and-table-lookup method 82 * to do the combined operations quickly, assuming that RANGE_CENTER 83 * (defined in jpegint.h) is a power of 2. See the comments with 84 * prepare_range_limit_table (in jdmaster.c) for more info. 85 */ 86 87 #define RANGE_MASK (RANGE_CENTER * 2 - 1) 88 #define RANGE_SUBSET (RANGE_CENTER - CENTERJSAMPLE) 89 90 #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit - RANGE_SUBSET) 91 92 93 /* Short forms of external names for systems with brain-damaged linkers. */ 94 95 #ifdef NEED_SHORT_EXTERNAL_NAMES 96 #define jpeg_fdct_islow jFDislow 97 #define jpeg_fdct_ifast jFDifast 98 #define jpeg_fdct_float jFDfloat 99 #define jpeg_fdct_7x7 jFD7x7 100 #define jpeg_fdct_6x6 jFD6x6 101 #define jpeg_fdct_5x5 jFD5x5 102 #define jpeg_fdct_4x4 jFD4x4 103 #define jpeg_fdct_3x3 jFD3x3 104 #define jpeg_fdct_2x2 jFD2x2 105 #define jpeg_fdct_1x1 jFD1x1 106 #define jpeg_fdct_9x9 jFD9x9 107 #define jpeg_fdct_10x10 jFD10x10 108 #define jpeg_fdct_11x11 jFD11x11 109 #define jpeg_fdct_12x12 jFD12x12 110 #define jpeg_fdct_13x13 jFD13x13 111 #define jpeg_fdct_14x14 jFD14x14 112 #define jpeg_fdct_15x15 jFD15x15 113 #define jpeg_fdct_16x16 jFD16x16 114 #define jpeg_fdct_16x8 jFD16x8 115 #define jpeg_fdct_14x7 jFD14x7 116 #define jpeg_fdct_12x6 jFD12x6 117 #define jpeg_fdct_10x5 jFD10x5 118 #define jpeg_fdct_8x4 jFD8x4 119 #define jpeg_fdct_6x3 jFD6x3 120 #define jpeg_fdct_4x2 jFD4x2 121 #define jpeg_fdct_2x1 jFD2x1 122 #define jpeg_fdct_8x16 jFD8x16 123 #define jpeg_fdct_7x14 jFD7x14 124 #define jpeg_fdct_6x12 jFD6x12 125 #define jpeg_fdct_5x10 jFD5x10 126 #define jpeg_fdct_4x8 jFD4x8 127 #define jpeg_fdct_3x6 jFD3x6 128 #define jpeg_fdct_2x4 jFD2x4 129 #define jpeg_fdct_1x2 jFD1x2 130 #define jpeg_idct_islow jRDislow 131 #define jpeg_idct_ifast jRDifast 132 #define jpeg_idct_float jRDfloat 133 #define jpeg_idct_7x7 jRD7x7 134 #define jpeg_idct_6x6 jRD6x6 135 #define jpeg_idct_5x5 jRD5x5 136 #define jpeg_idct_4x4 jRD4x4 137 #define jpeg_idct_3x3 jRD3x3 138 #define jpeg_idct_2x2 jRD2x2 139 #define jpeg_idct_1x1 jRD1x1 140 #define jpeg_idct_9x9 jRD9x9 141 #define jpeg_idct_10x10 jRD10x10 142 #define jpeg_idct_11x11 jRD11x11 143 #define jpeg_idct_12x12 jRD12x12 144 #define jpeg_idct_13x13 jRD13x13 145 #define jpeg_idct_14x14 jRD14x14 146 #define jpeg_idct_15x15 jRD15x15 147 #define jpeg_idct_16x16 jRD16x16 148 #define jpeg_idct_16x8 jRD16x8 149 #define jpeg_idct_14x7 jRD14x7 150 #define jpeg_idct_12x6 jRD12x6 151 #define jpeg_idct_10x5 jRD10x5 152 #define jpeg_idct_8x4 jRD8x4 153 #define jpeg_idct_6x3 jRD6x3 154 #define jpeg_idct_4x2 jRD4x2 155 #define jpeg_idct_2x1 jRD2x1 156 #define jpeg_idct_8x16 jRD8x16 157 #define jpeg_idct_7x14 jRD7x14 158 #define jpeg_idct_6x12 jRD6x12 159 #define jpeg_idct_5x10 jRD5x10 160 #define jpeg_idct_4x8 jRD4x8 161 #define jpeg_idct_3x6 jRD3x8 162 #define jpeg_idct_2x4 jRD2x4 163 #define jpeg_idct_1x2 jRD1x2 164 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 165 166 /* Extern declarations for the forward and inverse DCT routines. */ 167 168 EXTERN(void) jpeg_fdct_islow 169 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 170 EXTERN(void) jpeg_fdct_ifast 171 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 172 EXTERN(void) jpeg_fdct_float 173 JPP((FAST_FLOAT * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 174 EXTERN(void) jpeg_fdct_7x7 175 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 176 EXTERN(void) jpeg_fdct_6x6 177 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 178 EXTERN(void) jpeg_fdct_5x5 179 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 180 EXTERN(void) jpeg_fdct_4x4 181 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 182 EXTERN(void) jpeg_fdct_3x3 183 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 184 EXTERN(void) jpeg_fdct_2x2 185 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 186 EXTERN(void) jpeg_fdct_1x1 187 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 188 EXTERN(void) jpeg_fdct_9x9 189 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 190 EXTERN(void) jpeg_fdct_10x10 191 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 192 EXTERN(void) jpeg_fdct_11x11 193 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 194 EXTERN(void) jpeg_fdct_12x12 195 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 196 EXTERN(void) jpeg_fdct_13x13 197 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 198 EXTERN(void) jpeg_fdct_14x14 199 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 200 EXTERN(void) jpeg_fdct_15x15 201 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 202 EXTERN(void) jpeg_fdct_16x16 203 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 204 EXTERN(void) jpeg_fdct_16x8 205 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 206 EXTERN(void) jpeg_fdct_14x7 207 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 208 EXTERN(void) jpeg_fdct_12x6 209 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 210 EXTERN(void) jpeg_fdct_10x5 211 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 212 EXTERN(void) jpeg_fdct_8x4 213 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 214 EXTERN(void) jpeg_fdct_6x3 215 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 216 EXTERN(void) jpeg_fdct_4x2 217 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 218 EXTERN(void) jpeg_fdct_2x1 219 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 220 EXTERN(void) jpeg_fdct_8x16 221 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 222 EXTERN(void) jpeg_fdct_7x14 223 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 224 EXTERN(void) jpeg_fdct_6x12 225 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 226 EXTERN(void) jpeg_fdct_5x10 227 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 228 EXTERN(void) jpeg_fdct_4x8 229 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 230 EXTERN(void) jpeg_fdct_3x6 231 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 232 EXTERN(void) jpeg_fdct_2x4 233 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 234 EXTERN(void) jpeg_fdct_1x2 235 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)); 236 237 EXTERN(void) jpeg_idct_islow 238 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 239 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 240 EXTERN(void) jpeg_idct_ifast 241 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 242 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 243 EXTERN(void) jpeg_idct_float 244 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 245 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 246 EXTERN(void) jpeg_idct_7x7 247 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 248 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 249 EXTERN(void) jpeg_idct_6x6 250 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 251 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 252 EXTERN(void) jpeg_idct_5x5 253 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 254 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 255 EXTERN(void) jpeg_idct_4x4 256 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 257 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 258 EXTERN(void) jpeg_idct_3x3 259 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 260 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 261 EXTERN(void) jpeg_idct_2x2 262 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 263 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 264 EXTERN(void) jpeg_idct_1x1 265 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 266 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 267 EXTERN(void) jpeg_idct_9x9 268 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 269 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 270 EXTERN(void) jpeg_idct_10x10 271 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 272 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 273 EXTERN(void) jpeg_idct_11x11 274 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 275 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 276 EXTERN(void) jpeg_idct_12x12 277 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 278 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 279 EXTERN(void) jpeg_idct_13x13 280 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 281 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 282 EXTERN(void) jpeg_idct_14x14 283 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 284 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 285 EXTERN(void) jpeg_idct_15x15 286 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 287 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 288 EXTERN(void) jpeg_idct_16x16 289 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 290 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 291 EXTERN(void) jpeg_idct_16x8 292 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 293 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 294 EXTERN(void) jpeg_idct_14x7 295 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 296 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 297 EXTERN(void) jpeg_idct_12x6 298 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 299 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 300 EXTERN(void) jpeg_idct_10x5 301 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 302 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 303 EXTERN(void) jpeg_idct_8x4 304 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 305 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 306 EXTERN(void) jpeg_idct_6x3 307 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 308 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 309 EXTERN(void) jpeg_idct_4x2 310 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 311 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 312 EXTERN(void) jpeg_idct_2x1 313 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 314 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 315 EXTERN(void) jpeg_idct_8x16 316 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 317 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 318 EXTERN(void) jpeg_idct_7x14 319 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 320 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 321 EXTERN(void) jpeg_idct_6x12 322 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 323 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 324 EXTERN(void) jpeg_idct_5x10 325 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 326 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 327 EXTERN(void) jpeg_idct_4x8 328 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 329 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 330 EXTERN(void) jpeg_idct_3x6 331 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 332 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 333 EXTERN(void) jpeg_idct_2x4 334 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 335 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 336 EXTERN(void) jpeg_idct_1x2 337 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 338 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 339 340 341 /* 342 * Macros for handling fixed-point arithmetic; these are used by many 343 * but not all of the DCT/IDCT modules. 344 * 345 * All values are expected to be of type INT32. 346 * Fractional constants are scaled left by CONST_BITS bits. 347 * CONST_BITS is defined within each module using these macros, 348 * and may differ from one module to the next. 349 */ 350 351 #define ONE ((INT32) 1) 352 #define CONST_SCALE (ONE << CONST_BITS) 353 354 /* Convert a positive real constant to an integer scaled by CONST_SCALE. 355 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, 356 * thus causing a lot of useless floating-point operations at run time. 357 */ 358 359 #define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5)) 360 361 /* Descale and correctly round an INT32 value that's scaled by N bits. 362 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding 363 * the fudge factor is correct for either sign of X. 364 */ 365 366 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) 367 368 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. 369 * This macro is used only when the two inputs will actually be no more than 370 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a 371 * full 32x32 multiply. This provides a useful speedup on many machines. 372 * Unfortunately there is no way to specify a 16x16->32 multiply portably 373 * in C, but some C compilers will do the right thing if you provide the 374 * correct combination of casts. 375 */ 376 377 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 378 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const))) 379 #endif 380 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ 381 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const))) 382 #endif 383 384 #ifndef MULTIPLY16C16 /* default definition */ 385 #define MULTIPLY16C16(var,const) ((var) * (const)) 386 #endif 387 388 /* Same except both inputs are variables. */ 389 390 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 391 #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2))) 392 #endif 393 394 #ifndef MULTIPLY16V16 /* default definition */ 395 #define MULTIPLY16V16(var1,var2) ((var1) * (var2)) 396 #endif 397 398 /* Like RIGHT_SHIFT, but applies to a DCTELEM. 399 * We assume that int right shift is unsigned if INT32 right shift is. 400 */ 401 402 #ifdef RIGHT_SHIFT_IS_UNSIGNED 403 #define ISHIFT_TEMPS DCTELEM ishift_temp; 404 #if BITS_IN_JSAMPLE == 8 405 #define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */ 406 #else 407 #define DCTELEMBITS 32 /* DCTELEM must be 32 bits */ 408 #endif 409 #define IRIGHT_SHIFT(x,shft) \ 410 ((ishift_temp = (x)) < 0 ? \ 411 (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \ 412 (ishift_temp >> (shft))) 413 #else 414 #define ISHIFT_TEMPS 415 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) 416 #endif 417