1 #if !defined(_FX_JPEG_TURBO_) 2 /* 3 * jidctred.c 4 * 5 * Copyright (C) 1994-1998, Thomas G. Lane. 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 inverse-DCT routines that produce reduced-size output: 10 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block. 11 * 12 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M) 13 * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step 14 * with an 8-to-4 step that produces the four averages of two adjacent outputs 15 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output). 16 * These steps were derived by computing the corresponding values at the end 17 * of the normal LL&M code, then simplifying as much as possible. 18 * 19 * 1x1 is trivial: just take the DC coefficient divided by 8. 20 * 21 * See jidctint.c for additional comments. 22 */ 23 24 #define JPEG_INTERNALS 25 #include "jinclude.h" 26 #include "jpeglib.h" 27 #include "jdct.h" /* Private declarations for DCT subsystem */ 28 29 #ifdef IDCT_SCALING_SUPPORTED 30 31 32 /* 33 * This module is specialized to the case DCTSIZE = 8. 34 */ 35 36 #if DCTSIZE != 8 37 Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ 38 #endif 39 40 41 /* Scaling is the same as in jidctint.c. */ 42 43 #if BITS_IN_JSAMPLE == 8 44 #define CONST_BITS 13 45 #define PASS1_BITS 2 46 #else 47 #define CONST_BITS 13 48 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */ 49 #endif 50 51 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus 52 * causing a lot of useless floating-point operations at run time. 53 * To get around this we use the following pre-calculated constants. 54 * If you change CONST_BITS you may want to add appropriate values. 55 * (With a reasonable C compiler, you can just rely on the FIX() macro...) 56 */ 57 58 #if CONST_BITS == 13 59 #define FIX_0_211164243 ((INT32) 1730) /* FIX(0.211164243) */ 60 #define FIX_0_509795579 ((INT32) 4176) /* FIX(0.509795579) */ 61 #define FIX_0_601344887 ((INT32) 4926) /* FIX(0.601344887) */ 62 #define FIX_0_720959822 ((INT32) 5906) /* FIX(0.720959822) */ 63 #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */ 64 #define FIX_0_850430095 ((INT32) 6967) /* FIX(0.850430095) */ 65 #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */ 66 #define FIX_1_061594337 ((INT32) 8697) /* FIX(1.061594337) */ 67 #define FIX_1_272758580 ((INT32) 10426) /* FIX(1.272758580) */ 68 #define FIX_1_451774981 ((INT32) 11893) /* FIX(1.451774981) */ 69 #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */ 70 #define FIX_2_172734803 ((INT32) 17799) /* FIX(2.172734803) */ 71 #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */ 72 #define FIX_3_624509785 ((INT32) 29692) /* FIX(3.624509785) */ 73 #else 74 #define FIX_0_211164243 FIX(0.211164243) 75 #define FIX_0_509795579 FIX(0.509795579) 76 #define FIX_0_601344887 FIX(0.601344887) 77 #define FIX_0_720959822 FIX(0.720959822) 78 #define FIX_0_765366865 FIX(0.765366865) 79 #define FIX_0_850430095 FIX(0.850430095) 80 #define FIX_0_899976223 FIX(0.899976223) 81 #define FIX_1_061594337 FIX(1.061594337) 82 #define FIX_1_272758580 FIX(1.272758580) 83 #define FIX_1_451774981 FIX(1.451774981) 84 #define FIX_1_847759065 FIX(1.847759065) 85 #define FIX_2_172734803 FIX(2.172734803) 86 #define FIX_2_562915447 FIX(2.562915447) 87 #define FIX_3_624509785 FIX(3.624509785) 88 #endif 89 90 91 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. 92 * For 8-bit samples with the recommended scaling, all the variable 93 * and constant values involved are no more than 16 bits wide, so a 94 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply. 95 * For 12-bit samples, a full 32-bit multiplication will be needed. 96 */ 97 98 #if BITS_IN_JSAMPLE == 8 99 #define MULTIPLY(var,const) MULTIPLY16C16(var,const) 100 #else 101 #define MULTIPLY(var,const) ((var) * (const)) 102 #endif 103 104 105 /* Dequantize a coefficient by multiplying it by the multiplier-table 106 * entry; produce an int result. In this module, both inputs and result 107 * are 16 bits or less, so either int or short multiply will work. 108 */ 109 110 #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) 111 112 113 /* 114 * Perform dequantization and inverse DCT on one block of coefficients, 115 * producing a reduced-size 4x4 output block. 116 */ 117 118 GLOBAL(void) 119 jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 120 JCOEFPTR coef_block, 121 JSAMPARRAY output_buf, JDIMENSION output_col) 122 { 123 INT32 tmp0, tmp2, tmp10, tmp12; 124 INT32 z1, z2, z3, z4; 125 JCOEFPTR inptr; 126 ISLOW_MULT_TYPE * quantptr; 127 int * wsptr; 128 JSAMPROW outptr; 129 JSAMPLE *range_limit = IDCT_range_limit(cinfo); 130 int ctr; 131 int workspace[DCTSIZE*4]; /* buffers data between passes */ 132 SHIFT_TEMPS 133 134 /* Pass 1: process columns from input, store into work array. */ 135 136 inptr = coef_block; 137 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; 138 wsptr = workspace; 139 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { 140 /* Don't bother to process column 4, because second pass won't use it */ 141 if (ctr == DCTSIZE-4) 142 continue; 143 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && 144 inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 && 145 inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) { 146 /* AC terms all zero; we need not examine term 4 for 4x4 output */ 147 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS; 148 149 wsptr[DCTSIZE*0] = dcval; 150 wsptr[DCTSIZE*1] = dcval; 151 wsptr[DCTSIZE*2] = dcval; 152 wsptr[DCTSIZE*3] = dcval; 153 154 continue; 155 } 156 157 /* Even part */ 158 159 tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); 160 tmp0 <<= (CONST_BITS+1); 161 162 z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); 163 z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); 164 165 tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865); 166 167 tmp10 = tmp0 + tmp2; 168 tmp12 = tmp0 - tmp2; 169 170 /* Odd part */ 171 172 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); 173 z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); 174 z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); 175 z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); 176 177 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ 178 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ 179 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ 180 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ 181 182 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ 183 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ 184 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ 185 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ 186 187 /* Final output stage */ 188 189 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); 190 wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); 191 wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); 192 wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); 193 } 194 195 /* Pass 2: process 4 rows from work array, store into output array. */ 196 197 wsptr = workspace; 198 for (ctr = 0; ctr < 4; ctr++) { 199 outptr = output_buf[ctr] + output_col; 200 /* It's not clear whether a zero row test is worthwhile here ... */ 201 202 #ifndef NO_ZERO_ROW_TEST 203 if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && 204 wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { 205 /* AC terms all zero */ 206 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) 207 & RANGE_MASK]; 208 209 outptr[0] = dcval; 210 outptr[1] = dcval; 211 outptr[2] = dcval; 212 outptr[3] = dcval; 213 214 wsptr += DCTSIZE; /* advance pointer to next row */ 215 continue; 216 } 217 #endif 218 219 /* Even part */ 220 221 tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1); 222 223 tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065) 224 + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865); 225 226 tmp10 = tmp0 + tmp2; 227 tmp12 = tmp0 - tmp2; 228 229 /* Odd part */ 230 231 z1 = (INT32) wsptr[7]; 232 z2 = (INT32) wsptr[5]; 233 z3 = (INT32) wsptr[3]; 234 z4 = (INT32) wsptr[1]; 235 236 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ 237 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ 238 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ 239 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ 240 241 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ 242 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ 243 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ 244 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ 245 246 /* Final output stage */ 247 248 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2, 249 CONST_BITS+PASS1_BITS+3+1) 250 & RANGE_MASK]; 251 outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2, 252 CONST_BITS+PASS1_BITS+3+1) 253 & RANGE_MASK]; 254 outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0, 255 CONST_BITS+PASS1_BITS+3+1) 256 & RANGE_MASK]; 257 outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0, 258 CONST_BITS+PASS1_BITS+3+1) 259 & RANGE_MASK]; 260 261 wsptr += DCTSIZE; /* advance pointer to next row */ 262 } 263 } 264 265 266 /* 267 * Perform dequantization and inverse DCT on one block of coefficients, 268 * producing a reduced-size 2x2 output block. 269 */ 270 271 GLOBAL(void) 272 jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 273 JCOEFPTR coef_block, 274 JSAMPARRAY output_buf, JDIMENSION output_col) 275 { 276 INT32 tmp0, tmp10, z1; 277 JCOEFPTR inptr; 278 ISLOW_MULT_TYPE * quantptr; 279 int * wsptr; 280 JSAMPROW outptr; 281 JSAMPLE *range_limit = IDCT_range_limit(cinfo); 282 int ctr; 283 int workspace[DCTSIZE*2]; /* buffers data between passes */ 284 SHIFT_TEMPS 285 286 /* Pass 1: process columns from input, store into work array. */ 287 288 inptr = coef_block; 289 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; 290 wsptr = workspace; 291 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { 292 /* Don't bother to process columns 2,4,6 */ 293 if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6) 294 continue; 295 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 && 296 inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) { 297 /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */ 298 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS; 299 300 wsptr[DCTSIZE*0] = dcval; 301 wsptr[DCTSIZE*1] = dcval; 302 303 continue; 304 } 305 306 /* Even part */ 307 308 z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); 309 tmp10 = z1 << (CONST_BITS+2); 310 311 /* Odd part */ 312 313 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); 314 tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */ 315 z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); 316 tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */ 317 z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); 318 tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */ 319 z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); 320 tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ 321 322 /* Final output stage */ 323 324 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2); 325 wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2); 326 } 327 328 /* Pass 2: process 2 rows from work array, store into output array. */ 329 330 wsptr = workspace; 331 for (ctr = 0; ctr < 2; ctr++) { 332 outptr = output_buf[ctr] + output_col; 333 /* It's not clear whether a zero row test is worthwhile here ... */ 334 335 #ifndef NO_ZERO_ROW_TEST 336 if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) { 337 /* AC terms all zero */ 338 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) 339 & RANGE_MASK]; 340 341 outptr[0] = dcval; 342 outptr[1] = dcval; 343 344 wsptr += DCTSIZE; /* advance pointer to next row */ 345 continue; 346 } 347 #endif 348 349 /* Even part */ 350 351 tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2); 352 353 /* Odd part */ 354 355 tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */ 356 + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */ 357 + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */ 358 + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ 359 360 /* Final output stage */ 361 362 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0, 363 CONST_BITS+PASS1_BITS+3+2) 364 & RANGE_MASK]; 365 outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0, 366 CONST_BITS+PASS1_BITS+3+2) 367 & RANGE_MASK]; 368 369 wsptr += DCTSIZE; /* advance pointer to next row */ 370 } 371 } 372 373 374 /* 375 * Perform dequantization and inverse DCT on one block of coefficients, 376 * producing a reduced-size 1x1 output block. 377 */ 378 379 GLOBAL(void) 380 jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 381 JCOEFPTR coef_block, 382 JSAMPARRAY output_buf, JDIMENSION output_col) 383 { 384 int dcval; 385 ISLOW_MULT_TYPE * quantptr; 386 JSAMPLE *range_limit = IDCT_range_limit(cinfo); 387 SHIFT_TEMPS 388 389 /* We hardly need an inverse DCT routine for this: just take the 390 * average pixel value, which is one-eighth of the DC coefficient. 391 */ 392 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; 393 dcval = DEQUANTIZE(coef_block[0], quantptr[0]); 394 dcval = (int) DESCALE((INT32) dcval, 3); 395 396 output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; 397 } 398 399 #endif /* IDCT_SCALING_SUPPORTED */ 400 401 #endif //_FX_JPEG_TURBO_ 402
