| 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_BITS;
|
|---|
| 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_BITS;
|
|---|
| 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+c7) */
|
|---|
| 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+c7) */
|
|---|
| 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 */
|
|---|
