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| 1 /* | |
| 2 * jidctred.c | |
| 3 * | |
| 4 * Copyright (C) 1994-1998, Thomas G. Lane. | |
| 5 * This file is part of the Independent JPEG Group's software. | |
| 6 * For conditions of distribution and use, see the accompanying README file. | |
| 7 * | |
| 8 * This file contains inverse-DCT routines that produce reduced-size output: | |
| 9 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block. | |
| 10 * | |
| 11 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M) | |
| 12 * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step | |
| 13 * with an 8-to-4 step that produces the four averages of two adjacent outputs | |
| 14 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output). | |
| 15 * These steps were derived by computing the corresponding values at the end | |
| 16 * of the normal LL&M code, then simplifying as much as possible. | |
| 17 * | |
| 18 * 1x1 is trivial: just take the DC coefficient divided by 8. | |
| 19 * | |
| 20 * See jidctint.c for additional comments. | |
| 21 */ | |
| 22 | |
| 23 #define JPEG_INTERNALS | |
| 24 #include "jinclude.h" | |
| 25 #include "jpeglib.h" | |
| 26 #include "jdct.h" /* Private declarations for DCT subsystem */ | |
| 27 | |
| 28 #ifdef IDCT_SCALING_SUPPORTED | |
| 29 | |
| 30 | |
| 31 /* | |
| 32 * This module is specialized to the case DCTSIZE = 8. | |
| 33 */ | |
| 34 | |
| 35 #if DCTSIZE != 8 | |
| 36 Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ | |
| 37 #endif | |
| 38 | |
| 39 | |
| 40 /* Scaling is the same as in jidctint.c. */ | |
| 41 | |
| 42 #if BITS_IN_JSAMPLE == 8 | |
| 43 #define CONST_BITS 13 | |
| 44 #define PASS1_BITS 2 | |
| 45 #else | |
| 46 #define CONST_BITS 13 | |
| 47 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */ | |
| 48 #endif | |
| 49 | |
| 50 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus | |
| 51 * causing a lot of useless floating-point operations at run time. | |
| 52 * To get around this we use the following pre-calculated constants. | |
| 53 * If you change CONST_BITS you may want to add appropriate values. | |
| 54 * (With a reasonable C compiler, you can just rely on the FIX() macro...) | |
| 55 */ | |
| 56 | |
| 57 #if CONST_BITS == 13 | |
| 58 #define FIX_0_211164243 ((INT32) 1730) /* FIX(0.211164243) */ | |
| 59 #define FIX_0_509795579 ((INT32) 4176) /* FIX(0.509795579) */ | |
| 60 #define FIX_0_601344887 ((INT32) 4926) /* FIX(0.601344887) */ | |
| 61 #define FIX_0_720959822 ((INT32) 5906) /* FIX(0.720959822) */ | |
| 62 #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */ | |
| 63 #define FIX_0_850430095 ((INT32) 6967) /* FIX(0.850430095) */ | |
| 64 #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */ | |
| 65 #define FIX_1_061594337 ((INT32) 8697) /* FIX(1.061594337) */ | |
| 66 #define FIX_1_272758580 ((INT32) 10426) /* FIX(1.272758580) */ | |
| 67 #define FIX_1_451774981 ((INT32) 11893) /* FIX(1.451774981) */ | |
| 68 #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */ | |
| 69 #define FIX_2_172734803 ((INT32) 17799) /* FIX(2.172734803) */ | |
| 70 #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */ | |
| 71 #define FIX_3_624509785 ((INT32) 29692) /* FIX(3.624509785) */ | |
| 72 #else | |
| 73 #define FIX_0_211164243 FIX(0.211164243) | |
| 74 #define FIX_0_509795579 FIX(0.509795579) | |
| 75 #define FIX_0_601344887 FIX(0.601344887) | |
| 76 #define FIX_0_720959822 FIX(0.720959822) | |
| 77 #define FIX_0_765366865 FIX(0.765366865) | |
| 78 #define FIX_0_850430095 FIX(0.850430095) | |
| 79 #define FIX_0_899976223 FIX(0.899976223) | |
| 80 #define FIX_1_061594337 FIX(1.061594337) | |
| 81 #define FIX_1_272758580 FIX(1.272758580) | |
| 82 #define FIX_1_451774981 FIX(1.451774981) | |
| 83 #define FIX_1_847759065 FIX(1.847759065) | |
| 84 #define FIX_2_172734803 FIX(2.172734803) | |
| 85 #define FIX_2_562915447 FIX(2.562915447) | |
| 86 #define FIX_3_624509785 FIX(3.624509785) | |
| 87 #endif | |
| 88 | |
| 89 | |
| 90 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. | |
| 91 * For 8-bit samples with the recommended scaling, all the variable | |
| 92 * and constant values involved are no more than 16 bits wide, so a | |
| 93 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply. | |
| 94 * For 12-bit samples, a full 32-bit multiplication will be needed. | |
| 95 */ | |
| 96 | |
| 97 #if BITS_IN_JSAMPLE == 8 | |
| 98 #define MULTIPLY(var,const) MULTIPLY16C16(var,const) | |
| 99 #else | |
| 100 #define MULTIPLY(var,const) ((var) * (const)) | |
| 101 #endif | |
| 102 | |
| 103 | |
| 104 /* Dequantize a coefficient by multiplying it by the multiplier-table | |
| 105 * entry; produce an int result. In this module, both inputs and result | |
| 106 * are 16 bits or less, so either int or short multiply will work. | |
| 107 */ | |
| 108 | |
| 109 #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) | |
| 110 | |
| 111 | |
| 112 /* | |
| 113 * Perform dequantization and inverse DCT on one block of coefficients, | |
| 114 * producing a reduced-size 4x4 output block. | |
| 115 */ | |
| 116 | |
| 117 GLOBAL(void) | |
| 118 jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr, | |
| 119 JCOEFPTR coef_block, | |
| 120 JSAMPARRAY output_buf, JDIMENSION output_col) | |
| 121 { | |
| 122 INT32 tmp0, tmp2, tmp10, tmp12; | |
| 123 INT32 z1, z2, z3, z4; | |
| 124 JCOEFPTR inptr; | |
| 125 ISLOW_MULT_TYPE * quantptr; | |
| 126 int * wsptr; | |
| 127 JSAMPROW outptr; | |
| 128 JSAMPLE *range_limit = IDCT_range_limit(cinfo); | |
| 129 int ctr; | |
| 130 int workspace[DCTSIZE*4]; /* buffers data between passes */ | |
| 131 SHIFT_TEMPS | |
| 132 | |
| 133 /* Pass 1: process columns from input, store into work array. */ | |
| 134 | |
| 135 inptr = coef_block; | |
| 136 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; | |
| 137 wsptr = workspace; | |
| 138 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { | |
| 139 /* Don't bother to process column 4, because second pass won't use it */ | |
| 140 if (ctr == DCTSIZE-4) | |
| 141 continue; | |
| 142 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && | |
| 143 inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 && | |
| 144 inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) { | |
| 145 /* AC terms all zero; we need not examine term 4 for 4x4 output */ | |
| 146 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BIT
S; | |
| 147 | |
| 148 wsptr[DCTSIZE*0] = dcval; | |
| 149 wsptr[DCTSIZE*1] = dcval; | |
| 150 wsptr[DCTSIZE*2] = dcval; | |
| 151 wsptr[DCTSIZE*3] = dcval; | |
| 152 | |
| 153 continue; | |
| 154 } | |
| 155 | |
| 156 /* Even part */ | |
| 157 | |
| 158 tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); | |
| 159 tmp0 <<= (CONST_BITS+1); | |
| 160 | |
| 161 z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); | |
| 162 z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); | |
| 163 | |
| 164 tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865); | |
| 165 | |
| 166 tmp10 = tmp0 + tmp2; | |
| 167 tmp12 = tmp0 - tmp2; | |
| 168 | |
| 169 /* Odd part */ | |
| 170 | |
| 171 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); | |
| 172 z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); | |
| 173 z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); | |
| 174 z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); | |
| 175 | |
| 176 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ | |
| 177 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ | |
| 178 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ | |
| 179 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ | |
| 180 | |
| 181 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ | |
| 182 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ | |
| 183 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ | |
| 184 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ | |
| 185 | |
| 186 /* Final output stage */ | |
| 187 | |
| 188 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); | |
| 189 wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); | |
| 190 wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); | |
| 191 wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); | |
| 192 } | |
| 193 | |
| 194 /* Pass 2: process 4 rows from work array, store into output array. */ | |
| 195 | |
| 196 wsptr = workspace; | |
| 197 for (ctr = 0; ctr < 4; ctr++) { | |
| 198 outptr = output_buf[ctr] + output_col; | |
| 199 /* It's not clear whether a zero row test is worthwhile here ... */ | |
| 200 | |
| 201 #ifndef NO_ZERO_ROW_TEST | |
| 202 if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && | |
| 203 wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { | |
| 204 /* AC terms all zero */ | |
| 205 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) | |
| 206 & RANGE_MASK]; | |
| 207 | |
| 208 outptr[0] = dcval; | |
| 209 outptr[1] = dcval; | |
| 210 outptr[2] = dcval; | |
| 211 outptr[3] = dcval; | |
| 212 | |
| 213 wsptr += DCTSIZE; /* advance pointer to next row */ | |
| 214 continue; | |
| 215 } | |
| 216 #endif | |
| 217 | |
| 218 /* Even part */ | |
| 219 | |
| 220 tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1); | |
| 221 | |
| 222 tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065) | |
| 223 + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865); | |
| 224 | |
| 225 tmp10 = tmp0 + tmp2; | |
| 226 tmp12 = tmp0 - tmp2; | |
| 227 | |
| 228 /* Odd part */ | |
| 229 | |
| 230 z1 = (INT32) wsptr[7]; | |
| 231 z2 = (INT32) wsptr[5]; | |
| 232 z3 = (INT32) wsptr[3]; | |
| 233 z4 = (INT32) wsptr[1]; | |
| 234 | |
| 235 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ | |
| 236 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ | |
| 237 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ | |
| 238 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ | |
| 239 | |
| 240 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ | |
| 241 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ | |
| 242 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ | |
| 243 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ | |
| 244 | |
| 245 /* Final output stage */ | |
| 246 | |
| 247 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2, | |
| 248 CONST_BITS+PASS1_BITS+3+1) | |
| 249 & RANGE_MASK]; | |
| 250 outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2, | |
| 251 CONST_BITS+PASS1_BITS+3+1) | |
| 252 & RANGE_MASK]; | |
| 253 outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0, | |
| 254 CONST_BITS+PASS1_BITS+3+1) | |
| 255 & RANGE_MASK]; | |
| 256 outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0, | |
| 257 CONST_BITS+PASS1_BITS+3+1) | |
| 258 & RANGE_MASK]; | |
| 259 | |
| 260 wsptr += DCTSIZE; /* advance pointer to next row */ | |
| 261 } | |
| 262 } | |
| 263 | |
| 264 | |
| 265 /* | |
| 266 * Perform dequantization and inverse DCT on one block of coefficients, | |
| 267 * producing a reduced-size 2x2 output block. | |
| 268 */ | |
| 269 | |
| 270 GLOBAL(void) | |
| 271 jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr, | |
| 272 JCOEFPTR coef_block, | |
| 273 JSAMPARRAY output_buf, JDIMENSION output_col) | |
| 274 { | |
| 275 INT32 tmp0, tmp10, z1; | |
| 276 JCOEFPTR inptr; | |
| 277 ISLOW_MULT_TYPE * quantptr; | |
| 278 int * wsptr; | |
| 279 JSAMPROW outptr; | |
| 280 JSAMPLE *range_limit = IDCT_range_limit(cinfo); | |
| 281 int ctr; | |
| 282 int workspace[DCTSIZE*2]; /* buffers data between passes */ | |
| 283 SHIFT_TEMPS | |
| 284 | |
| 285 /* Pass 1: process columns from input, store into work array. */ | |
| 286 | |
| 287 inptr = coef_block; | |
| 288 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; | |
| 289 wsptr = workspace; | |
| 290 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { | |
| 291 /* Don't bother to process columns 2,4,6 */ | |
| 292 if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6) | |
| 293 continue; | |
| 294 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 && | |
| 295 inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) { | |
| 296 /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */ | |
| 297 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BIT
S; | |
| 298 | |
| 299 wsptr[DCTSIZE*0] = dcval; | |
| 300 wsptr[DCTSIZE*1] = dcval; | |
| 301 | |
| 302 continue; | |
| 303 } | |
| 304 | |
| 305 /* Even part */ | |
| 306 | |
| 307 z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); | |
| 308 tmp10 = z1 << (CONST_BITS+2); | |
| 309 | |
| 310 /* Odd part */ | |
| 311 | |
| 312 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); | |
| 313 tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */ | |
| 314 z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); | |
| 315 tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */ | |
| 316 z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); | |
| 317 tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */ | |
| 318 z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); | |
| 319 tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ | |
| 320 | |
| 321 /* Final output stage */ | |
| 322 | |
| 323 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2); | |
| 324 wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2); | |
| 325 } | |
| 326 | |
| 327 /* Pass 2: process 2 rows from work array, store into output array. */ | |
| 328 | |
| 329 wsptr = workspace; | |
| 330 for (ctr = 0; ctr < 2; ctr++) { | |
| 331 outptr = output_buf[ctr] + output_col; | |
| 332 /* It's not clear whether a zero row test is worthwhile here ... */ | |
| 333 | |
| 334 #ifndef NO_ZERO_ROW_TEST | |
| 335 if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) { | |
| 336 /* AC terms all zero */ | |
| 337 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) | |
| 338 & RANGE_MASK]; | |
| 339 | |
| 340 outptr[0] = dcval; | |
| 341 outptr[1] = dcval; | |
| 342 | |
| 343 wsptr += DCTSIZE; /* advance pointer to next row */ | |
| 344 continue; | |
| 345 } | |
| 346 #endif | |
| 347 | |
| 348 /* Even part */ | |
| 349 | |
| 350 tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2); | |
| 351 | |
| 352 /* Odd part */ | |
| 353 | |
| 354 tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-
c1) */ | |
| 355 + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c
7) */ | |
| 356 + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5
-c7) */ | |
| 357 + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c
7) */ | |
| 358 | |
| 359 /* Final output stage */ | |
| 360 | |
| 361 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0, | |
| 362 CONST_BITS+PASS1_BITS+3+2) | |
| 363 & RANGE_MASK]; | |
| 364 outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0, | |
| 365 CONST_BITS+PASS1_BITS+3+2) | |
| 366 & RANGE_MASK]; | |
| 367 | |
| 368 wsptr += DCTSIZE; /* advance pointer to next row */ | |
| 369 } | |
| 370 } | |
| 371 | |
| 372 | |
| 373 /* | |
| 374 * Perform dequantization and inverse DCT on one block of coefficients, | |
| 375 * producing a reduced-size 1x1 output block. | |
| 376 */ | |
| 377 | |
| 378 GLOBAL(void) | |
| 379 jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr, | |
| 380 JCOEFPTR coef_block, | |
| 381 JSAMPARRAY output_buf, JDIMENSION output_col) | |
| 382 { | |
| 383 int dcval; | |
| 384 ISLOW_MULT_TYPE * quantptr; | |
| 385 JSAMPLE *range_limit = IDCT_range_limit(cinfo); | |
| 386 SHIFT_TEMPS | |
| 387 | |
| 388 /* We hardly need an inverse DCT routine for this: just take the | |
| 389 * average pixel value, which is one-eighth of the DC coefficient. | |
| 390 */ | |
| 391 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; | |
| 392 dcval = DEQUANTIZE(coef_block[0], quantptr[0]); | |
| 393 dcval = (int) DESCALE((INT32) dcval, 3); | |
| 394 | |
| 395 output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; | |
| 396 } | |
| 397 | |
| 398 #endif /* IDCT_SCALING_SUPPORTED */ | |
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Chromium Code Reviews
Issue 1705523002:
Remove libjpeg and libjpeg_turbo. (Closed)
Base URL: https://github.com/domokit/mojo.git@master