Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 1 | /* |
| 2 | * jidctfst.c |
| 3 | * |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 4 | * This file was part of the Independent JPEG Group's software: |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 5 | * Copyright (C) 1994-1998, Thomas G. Lane. |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 6 | * libjpeg-turbo Modifications: |
| 7 | * Copyright (C) 2015, D. R. Commander. |
| 8 | * For conditions of distribution and use, see the accompanying README.ijg |
| 9 | * file. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 10 | * |
| 11 | * This file contains a fast, not so accurate integer implementation of the |
| 12 | * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine |
| 13 | * must also perform dequantization of the input coefficients. |
| 14 | * |
| 15 | * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT |
| 16 | * on each row (or vice versa, but it's more convenient to emit a row at |
| 17 | * a time). Direct algorithms are also available, but they are much more |
| 18 | * complex and seem not to be any faster when reduced to code. |
| 19 | * |
| 20 | * This implementation is based on Arai, Agui, and Nakajima's algorithm for |
| 21 | * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in |
| 22 | * Japanese, but the algorithm is described in the Pennebaker & Mitchell |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 23 | * JPEG textbook (see REFERENCES section in file README.ijg). The following |
| 24 | * code is based directly on figure 4-8 in P&M. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 25 | * While an 8-point DCT cannot be done in less than 11 multiplies, it is |
| 26 | * possible to arrange the computation so that many of the multiplies are |
| 27 | * simple scalings of the final outputs. These multiplies can then be |
| 28 | * folded into the multiplications or divisions by the JPEG quantization |
| 29 | * table entries. The AA&N method leaves only 5 multiplies and 29 adds |
| 30 | * to be done in the DCT itself. |
| 31 | * The primary disadvantage of this method is that with fixed-point math, |
| 32 | * accuracy is lost due to imprecise representation of the scaled |
| 33 | * quantization values. The smaller the quantization table entry, the less |
| 34 | * precise the scaled value, so this implementation does worse with high- |
| 35 | * quality-setting files than with low-quality ones. |
| 36 | */ |
| 37 | |
| 38 | #define JPEG_INTERNALS |
| 39 | #include "jinclude.h" |
| 40 | #include "jpeglib.h" |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 41 | #include "jdct.h" /* Private declarations for DCT subsystem */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 42 | |
| 43 | #ifdef DCT_IFAST_SUPPORTED |
| 44 | |
| 45 | |
| 46 | /* |
| 47 | * This module is specialized to the case DCTSIZE = 8. |
| 48 | */ |
| 49 | |
| 50 | #if DCTSIZE != 8 |
| 51 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
| 52 | #endif |
| 53 | |
| 54 | |
| 55 | /* Scaling decisions are generally the same as in the LL&M algorithm; |
| 56 | * see jidctint.c for more details. However, we choose to descale |
| 57 | * (right shift) multiplication products as soon as they are formed, |
| 58 | * rather than carrying additional fractional bits into subsequent additions. |
| 59 | * This compromises accuracy slightly, but it lets us save a few shifts. |
| 60 | * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) |
| 61 | * everywhere except in the multiplications proper; this saves a good deal |
| 62 | * of work on 16-bit-int machines. |
| 63 | * |
| 64 | * The dequantized coefficients are not integers because the AA&N scaling |
| 65 | * factors have been incorporated. We represent them scaled up by PASS1_BITS, |
| 66 | * so that the first and second IDCT rounds have the same input scaling. |
| 67 | * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to |
| 68 | * avoid a descaling shift; this compromises accuracy rather drastically |
| 69 | * for small quantization table entries, but it saves a lot of shifts. |
| 70 | * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway, |
| 71 | * so we use a much larger scaling factor to preserve accuracy. |
| 72 | * |
| 73 | * A final compromise is to represent the multiplicative constants to only |
| 74 | * 8 fractional bits, rather than 13. This saves some shifting work on some |
| 75 | * machines, and may also reduce the cost of multiplication (since there |
| 76 | * are fewer one-bits in the constants). |
| 77 | */ |
| 78 | |
| 79 | #if BITS_IN_JSAMPLE == 8 |
| 80 | #define CONST_BITS 8 |
| 81 | #define PASS1_BITS 2 |
| 82 | #else |
| 83 | #define CONST_BITS 8 |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 84 | #define PASS1_BITS 1 /* lose a little precision to avoid overflow */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 85 | #endif |
| 86 | |
| 87 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
| 88 | * causing a lot of useless floating-point operations at run time. |
| 89 | * To get around this we use the following pre-calculated constants. |
| 90 | * If you change CONST_BITS you may want to add appropriate values. |
| 91 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
| 92 | */ |
| 93 | |
| 94 | #if CONST_BITS == 8 |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 95 | #define FIX_1_082392200 ((JLONG) 277) /* FIX(1.082392200) */ |
| 96 | #define FIX_1_414213562 ((JLONG) 362) /* FIX(1.414213562) */ |
| 97 | #define FIX_1_847759065 ((JLONG) 473) /* FIX(1.847759065) */ |
| 98 | #define FIX_2_613125930 ((JLONG) 669) /* FIX(2.613125930) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 99 | #else |
| 100 | #define FIX_1_082392200 FIX(1.082392200) |
| 101 | #define FIX_1_414213562 FIX(1.414213562) |
| 102 | #define FIX_1_847759065 FIX(1.847759065) |
| 103 | #define FIX_2_613125930 FIX(2.613125930) |
| 104 | #endif |
| 105 | |
| 106 | |
| 107 | /* We can gain a little more speed, with a further compromise in accuracy, |
| 108 | * by omitting the addition in a descaling shift. This yields an incorrectly |
| 109 | * rounded result half the time... |
| 110 | */ |
| 111 | |
| 112 | #ifndef USE_ACCURATE_ROUNDING |
| 113 | #undef DESCALE |
| 114 | #define DESCALE(x,n) RIGHT_SHIFT(x, n) |
| 115 | #endif |
| 116 | |
| 117 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 118 | /* Multiply a DCTELEM variable by an JLONG constant, and immediately |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 119 | * descale to yield a DCTELEM result. |
| 120 | */ |
| 121 | |
| 122 | #define MULTIPLY(var,const) ((DCTELEM) DESCALE((var) * (const), CONST_BITS)) |
| 123 | |
| 124 | |
| 125 | /* Dequantize a coefficient by multiplying it by the multiplier-table |
| 126 | * entry; produce a DCTELEM result. For 8-bit data a 16x16->16 |
| 127 | * multiplication will do. For 12-bit data, the multiplier table is |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 128 | * declared JLONG, so a 32-bit multiply will be used. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 129 | */ |
| 130 | |
| 131 | #if BITS_IN_JSAMPLE == 8 |
| 132 | #define DEQUANTIZE(coef,quantval) (((IFAST_MULT_TYPE) (coef)) * (quantval)) |
| 133 | #else |
| 134 | #define DEQUANTIZE(coef,quantval) \ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 135 | DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 136 | #endif |
| 137 | |
| 138 | |
| 139 | /* Like DESCALE, but applies to a DCTELEM and produces an int. |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 140 | * We assume that int right shift is unsigned if JLONG right shift is. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 141 | */ |
| 142 | |
| 143 | #ifdef RIGHT_SHIFT_IS_UNSIGNED |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 144 | #define ISHIFT_TEMPS DCTELEM ishift_temp; |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 145 | #if BITS_IN_JSAMPLE == 8 |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 146 | #define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */ |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 147 | #else |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 148 | #define DCTELEMBITS 32 /* DCTELEM must be 32 bits */ |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 149 | #endif |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 150 | #define IRIGHT_SHIFT(x,shft) \ |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 151 | ((ishift_temp = (x)) < 0 ? \ |
| 152 | (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \ |
| 153 | (ishift_temp >> (shft))) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 154 | #else |
| 155 | #define ISHIFT_TEMPS |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 156 | #define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 157 | #endif |
| 158 | |
| 159 | #ifdef USE_ACCURATE_ROUNDING |
| 160 | #define IDESCALE(x,n) ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n)) |
| 161 | #else |
| 162 | #define IDESCALE(x,n) ((int) IRIGHT_SHIFT(x, n)) |
| 163 | #endif |
| 164 | |
| 165 | |
| 166 | /* |
| 167 | * Perform dequantization and inverse DCT on one block of coefficients. |
| 168 | */ |
| 169 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 170 | GLOBAL(void) |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 171 | jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info *compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 172 | JCOEFPTR coef_block, |
| 173 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 174 | { |
| 175 | DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
| 176 | DCTELEM tmp10, tmp11, tmp12, tmp13; |
| 177 | DCTELEM z5, z10, z11, z12, z13; |
| 178 | JCOEFPTR inptr; |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame] | 179 | IFAST_MULT_TYPE *quantptr; |
| 180 | int *wsptr; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 181 | JSAMPROW outptr; |
| 182 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 183 | int ctr; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 184 | int workspace[DCTSIZE2]; /* buffers data between passes */ |
| 185 | SHIFT_TEMPS /* for DESCALE */ |
| 186 | ISHIFT_TEMPS /* for IDESCALE */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 187 | |
| 188 | /* Pass 1: process columns from input, store into work array. */ |
| 189 | |
| 190 | inptr = coef_block; |
| 191 | quantptr = (IFAST_MULT_TYPE *) compptr->dct_table; |
| 192 | wsptr = workspace; |
| 193 | for (ctr = DCTSIZE; ctr > 0; ctr--) { |
| 194 | /* Due to quantization, we will usually find that many of the input |
| 195 | * coefficients are zero, especially the AC terms. We can exploit this |
| 196 | * by short-circuiting the IDCT calculation for any column in which all |
| 197 | * the AC terms are zero. In that case each output is equal to the |
| 198 | * DC coefficient (with scale factor as needed). |
| 199 | * With typical images and quantization tables, half or more of the |
| 200 | * column DCT calculations can be simplified this way. |
| 201 | */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 202 | |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 203 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 204 | inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 && |
| 205 | inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 && |
| 206 | inptr[DCTSIZE*7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 207 | /* AC terms all zero */ |
| 208 | int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
| 209 | |
| 210 | wsptr[DCTSIZE*0] = dcval; |
| 211 | wsptr[DCTSIZE*1] = dcval; |
| 212 | wsptr[DCTSIZE*2] = dcval; |
| 213 | wsptr[DCTSIZE*3] = dcval; |
| 214 | wsptr[DCTSIZE*4] = dcval; |
| 215 | wsptr[DCTSIZE*5] = dcval; |
| 216 | wsptr[DCTSIZE*6] = dcval; |
| 217 | wsptr[DCTSIZE*7] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 218 | |
| 219 | inptr++; /* advance pointers to next column */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 220 | quantptr++; |
| 221 | wsptr++; |
| 222 | continue; |
| 223 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 224 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 225 | /* Even part */ |
| 226 | |
| 227 | tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
| 228 | tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); |
| 229 | tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]); |
| 230 | tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); |
| 231 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 232 | tmp10 = tmp0 + tmp2; /* phase 3 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 233 | tmp11 = tmp0 - tmp2; |
| 234 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 235 | tmp13 = tmp1 + tmp3; /* phases 5-3 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 236 | tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */ |
| 237 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 238 | tmp0 = tmp10 + tmp13; /* phase 2 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 239 | tmp3 = tmp10 - tmp13; |
| 240 | tmp1 = tmp11 + tmp12; |
| 241 | tmp2 = tmp11 - tmp12; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 242 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 243 | /* Odd part */ |
| 244 | |
| 245 | tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); |
| 246 | tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); |
| 247 | tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); |
| 248 | tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); |
| 249 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 250 | z13 = tmp6 + tmp5; /* phase 6 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 251 | z10 = tmp6 - tmp5; |
| 252 | z11 = tmp4 + tmp7; |
| 253 | z12 = tmp4 - tmp7; |
| 254 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 255 | tmp7 = z11 + z13; /* phase 5 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 256 | tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */ |
| 257 | |
| 258 | z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */ |
| 259 | tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */ |
| 260 | tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */ |
| 261 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 262 | tmp6 = tmp12 - tmp7; /* phase 2 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 263 | tmp5 = tmp11 - tmp6; |
| 264 | tmp4 = tmp10 + tmp5; |
| 265 | |
| 266 | wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7); |
| 267 | wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7); |
| 268 | wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6); |
| 269 | wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6); |
| 270 | wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5); |
| 271 | wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5); |
| 272 | wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4); |
| 273 | wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4); |
| 274 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 275 | inptr++; /* advance pointers to next column */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 276 | quantptr++; |
| 277 | wsptr++; |
| 278 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 279 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 280 | /* Pass 2: process rows from work array, store into output array. */ |
| 281 | /* Note that we must descale the results by a factor of 8 == 2**3, */ |
| 282 | /* and also undo the PASS1_BITS scaling. */ |
| 283 | |
| 284 | wsptr = workspace; |
| 285 | for (ctr = 0; ctr < DCTSIZE; ctr++) { |
| 286 | outptr = output_buf[ctr] + output_col; |
| 287 | /* Rows of zeroes can be exploited in the same way as we did with columns. |
| 288 | * However, the column calculation has created many nonzero AC terms, so |
| 289 | * the simplification applies less often (typically 5% to 10% of the time). |
| 290 | * On machines with very fast multiplication, it's possible that the |
| 291 | * test takes more time than it's worth. In that case this section |
| 292 | * may be commented out. |
| 293 | */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 294 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 295 | #ifndef NO_ZERO_ROW_TEST |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 296 | if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 297 | wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 298 | /* AC terms all zero */ |
| 299 | JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 300 | & RANGE_MASK]; |
| 301 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 302 | outptr[0] = dcval; |
| 303 | outptr[1] = dcval; |
| 304 | outptr[2] = dcval; |
| 305 | outptr[3] = dcval; |
| 306 | outptr[4] = dcval; |
| 307 | outptr[5] = dcval; |
| 308 | outptr[6] = dcval; |
| 309 | outptr[7] = dcval; |
| 310 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 311 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 312 | continue; |
| 313 | } |
| 314 | #endif |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 315 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 316 | /* Even part */ |
| 317 | |
| 318 | tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]); |
| 319 | tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]); |
| 320 | |
| 321 | tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]); |
| 322 | tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 323 | - tmp13; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 324 | |
| 325 | tmp0 = tmp10 + tmp13; |
| 326 | tmp3 = tmp10 - tmp13; |
| 327 | tmp1 = tmp11 + tmp12; |
| 328 | tmp2 = tmp11 - tmp12; |
| 329 | |
| 330 | /* Odd part */ |
| 331 | |
| 332 | z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3]; |
| 333 | z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3]; |
| 334 | z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7]; |
| 335 | z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7]; |
| 336 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 337 | tmp7 = z11 + z13; /* phase 5 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 338 | tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */ |
| 339 | |
| 340 | z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */ |
| 341 | tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */ |
| 342 | tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */ |
| 343 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 344 | tmp6 = tmp12 - tmp7; /* phase 2 */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 345 | tmp5 = tmp11 - tmp6; |
| 346 | tmp4 = tmp10 + tmp5; |
| 347 | |
| 348 | /* Final output stage: scale down by a factor of 8 and range-limit */ |
| 349 | |
| 350 | outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 351 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 352 | outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 353 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 354 | outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 355 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 356 | outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 357 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 358 | outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 359 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 360 | outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 361 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 362 | outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 363 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 364 | outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 365 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 366 | |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 367 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 368 | } |
| 369 | } |
| 370 | |
| 371 | #endif /* DCT_IFAST_SUPPORTED */ |