Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 1 | /* |
| 2 | * jidctred.c |
| 3 | * |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [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. |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 6 | * libjpeg-turbo Modifications: |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 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 inverse-DCT routines that produce reduced-size output: |
| 12 | * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block. |
| 13 | * |
| 14 | * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M) |
| 15 | * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step |
| 16 | * with an 8-to-4 step that produces the four averages of two adjacent outputs |
| 17 | * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output). |
| 18 | * These steps were derived by computing the corresponding values at the end |
| 19 | * of the normal LL&M code, then simplifying as much as possible. |
| 20 | * |
| 21 | * 1x1 is trivial: just take the DC coefficient divided by 8. |
| 22 | * |
| 23 | * See jidctint.c for additional comments. |
| 24 | */ |
| 25 | |
| 26 | #define JPEG_INTERNALS |
| 27 | #include "jinclude.h" |
| 28 | #include "jpeglib.h" |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 29 | #include "jdct.h" /* Private declarations for DCT subsystem */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 30 | |
| 31 | #ifdef IDCT_SCALING_SUPPORTED |
| 32 | |
| 33 | |
| 34 | /* |
| 35 | * This module is specialized to the case DCTSIZE = 8. |
| 36 | */ |
| 37 | |
| 38 | #if DCTSIZE != 8 |
| 39 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
| 40 | #endif |
| 41 | |
| 42 | |
| 43 | /* Scaling is the same as in jidctint.c. */ |
| 44 | |
| 45 | #if BITS_IN_JSAMPLE == 8 |
| 46 | #define CONST_BITS 13 |
| 47 | #define PASS1_BITS 2 |
| 48 | #else |
| 49 | #define CONST_BITS 13 |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 50 | #define PASS1_BITS 1 /* lose a little precision to avoid overflow */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 51 | #endif |
| 52 | |
| 53 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
| 54 | * causing a lot of useless floating-point operations at run time. |
| 55 | * To get around this we use the following pre-calculated constants. |
| 56 | * If you change CONST_BITS you may want to add appropriate values. |
| 57 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
| 58 | */ |
| 59 | |
| 60 | #if CONST_BITS == 13 |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 61 | #define FIX_0_211164243 ((JLONG) 1730) /* FIX(0.211164243) */ |
| 62 | #define FIX_0_509795579 ((JLONG) 4176) /* FIX(0.509795579) */ |
| 63 | #define FIX_0_601344887 ((JLONG) 4926) /* FIX(0.601344887) */ |
| 64 | #define FIX_0_720959822 ((JLONG) 5906) /* FIX(0.720959822) */ |
| 65 | #define FIX_0_765366865 ((JLONG) 6270) /* FIX(0.765366865) */ |
| 66 | #define FIX_0_850430095 ((JLONG) 6967) /* FIX(0.850430095) */ |
| 67 | #define FIX_0_899976223 ((JLONG) 7373) /* FIX(0.899976223) */ |
| 68 | #define FIX_1_061594337 ((JLONG) 8697) /* FIX(1.061594337) */ |
| 69 | #define FIX_1_272758580 ((JLONG) 10426) /* FIX(1.272758580) */ |
| 70 | #define FIX_1_451774981 ((JLONG) 11893) /* FIX(1.451774981) */ |
| 71 | #define FIX_1_847759065 ((JLONG) 15137) /* FIX(1.847759065) */ |
| 72 | #define FIX_2_172734803 ((JLONG) 17799) /* FIX(2.172734803) */ |
| 73 | #define FIX_2_562915447 ((JLONG) 20995) /* FIX(2.562915447) */ |
| 74 | #define FIX_3_624509785 ((JLONG) 29692) /* FIX(3.624509785) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 75 | #else |
| 76 | #define FIX_0_211164243 FIX(0.211164243) |
| 77 | #define FIX_0_509795579 FIX(0.509795579) |
| 78 | #define FIX_0_601344887 FIX(0.601344887) |
| 79 | #define FIX_0_720959822 FIX(0.720959822) |
| 80 | #define FIX_0_765366865 FIX(0.765366865) |
| 81 | #define FIX_0_850430095 FIX(0.850430095) |
| 82 | #define FIX_0_899976223 FIX(0.899976223) |
| 83 | #define FIX_1_061594337 FIX(1.061594337) |
| 84 | #define FIX_1_272758580 FIX(1.272758580) |
| 85 | #define FIX_1_451774981 FIX(1.451774981) |
| 86 | #define FIX_1_847759065 FIX(1.847759065) |
| 87 | #define FIX_2_172734803 FIX(2.172734803) |
| 88 | #define FIX_2_562915447 FIX(2.562915447) |
| 89 | #define FIX_3_624509785 FIX(3.624509785) |
| 90 | #endif |
| 91 | |
| 92 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 93 | /* Multiply a JLONG variable by a JLONG constant to yield a JLONG result. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 94 | * For 8-bit samples with the recommended scaling, all the variable |
| 95 | * and constant values involved are no more than 16 bits wide, so a |
| 96 | * 16x16->32 bit multiply can be used instead of a full 32x32 multiply. |
| 97 | * For 12-bit samples, a full 32-bit multiplication will be needed. |
| 98 | */ |
| 99 | |
| 100 | #if BITS_IN_JSAMPLE == 8 |
| 101 | #define MULTIPLY(var,const) MULTIPLY16C16(var,const) |
| 102 | #else |
| 103 | #define MULTIPLY(var,const) ((var) * (const)) |
| 104 | #endif |
| 105 | |
| 106 | |
| 107 | /* Dequantize a coefficient by multiplying it by the multiplier-table |
| 108 | * entry; produce an int result. In this module, both inputs and result |
| 109 | * are 16 bits or less, so either int or short multiply will work. |
| 110 | */ |
| 111 | |
| 112 | #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) |
| 113 | |
| 114 | |
| 115 | /* |
| 116 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 117 | * producing a reduced-size 4x4 output block. |
| 118 | */ |
| 119 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 120 | GLOBAL(void) |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 121 | jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info *compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 122 | JCOEFPTR coef_block, |
| 123 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 124 | { |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 125 | JLONG tmp0, tmp2, tmp10, tmp12; |
| 126 | JLONG z1, z2, z3, z4; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 127 | JCOEFPTR inptr; |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 128 | ISLOW_MULT_TYPE *quantptr; |
| 129 | int *wsptr; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 130 | JSAMPROW outptr; |
| 131 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 132 | int ctr; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 133 | int workspace[DCTSIZE*4]; /* buffers data between passes */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 134 | SHIFT_TEMPS |
| 135 | |
| 136 | /* Pass 1: process columns from input, store into work array. */ |
| 137 | |
| 138 | inptr = coef_block; |
| 139 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 140 | wsptr = workspace; |
| 141 | for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { |
| 142 | /* Don't bother to process column 4, because second pass won't use it */ |
| 143 | if (ctr == DCTSIZE-4) |
| 144 | continue; |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 145 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 146 | inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 && |
| 147 | inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 148 | /* AC terms all zero; we need not examine term 4 for 4x4 output */ |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 149 | int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]), |
| 150 | PASS1_BITS); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 151 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 152 | wsptr[DCTSIZE*0] = dcval; |
| 153 | wsptr[DCTSIZE*1] = dcval; |
| 154 | wsptr[DCTSIZE*2] = dcval; |
| 155 | wsptr[DCTSIZE*3] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 156 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 157 | continue; |
| 158 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 159 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 160 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 161 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 162 | tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 163 | tmp0 = LEFT_SHIFT(tmp0, CONST_BITS+1); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 164 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 165 | z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); |
| 166 | z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); |
| 167 | |
| 168 | tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 169 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 170 | tmp10 = tmp0 + tmp2; |
| 171 | tmp12 = tmp0 - tmp2; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 172 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 173 | /* Odd part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 174 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 175 | z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); |
| 176 | z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); |
| 177 | z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); |
| 178 | z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 179 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 180 | tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 181 | + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ |
| 182 | + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ |
| 183 | + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ |
| 184 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 185 | tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 186 | + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ |
| 187 | + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ |
| 188 | + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 189 | |
| 190 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 191 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 192 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); |
| 193 | wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); |
| 194 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); |
| 195 | wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); |
| 196 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 197 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 198 | /* Pass 2: process 4 rows from work array, store into output array. */ |
| 199 | |
| 200 | wsptr = workspace; |
| 201 | for (ctr = 0; ctr < 4; ctr++) { |
| 202 | outptr = output_buf[ctr] + output_col; |
| 203 | /* It's not clear whether a zero row test is worthwhile here ... */ |
| 204 | |
| 205 | #ifndef NO_ZERO_ROW_TEST |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 206 | if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 207 | wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 208 | /* AC terms all zero */ |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 209 | JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 210 | & RANGE_MASK]; |
| 211 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 212 | outptr[0] = dcval; |
| 213 | outptr[1] = dcval; |
| 214 | outptr[2] = dcval; |
| 215 | outptr[3] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 216 | |
| 217 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 218 | continue; |
| 219 | } |
| 220 | #endif |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 221 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 222 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 223 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 224 | tmp0 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+1); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 225 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 226 | tmp2 = MULTIPLY((JLONG) wsptr[2], FIX_1_847759065) |
| 227 | + MULTIPLY((JLONG) wsptr[6], - FIX_0_765366865); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 228 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 229 | tmp10 = tmp0 + tmp2; |
| 230 | tmp12 = tmp0 - tmp2; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 231 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 232 | /* Odd part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 233 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 234 | z1 = (JLONG) wsptr[7]; |
| 235 | z2 = (JLONG) wsptr[5]; |
| 236 | z3 = (JLONG) wsptr[3]; |
| 237 | z4 = (JLONG) wsptr[1]; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 238 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 239 | tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 240 | + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ |
| 241 | + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ |
| 242 | + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ |
| 243 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 244 | tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 245 | + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ |
| 246 | + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ |
| 247 | + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 248 | |
| 249 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 250 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 251 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 252 | CONST_BITS+PASS1_BITS+3+1) |
| 253 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 254 | outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 255 | CONST_BITS+PASS1_BITS+3+1) |
| 256 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 257 | outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 258 | CONST_BITS+PASS1_BITS+3+1) |
| 259 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 260 | outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 261 | CONST_BITS+PASS1_BITS+3+1) |
| 262 | & RANGE_MASK]; |
| 263 | |
| 264 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 265 | } |
| 266 | } |
| 267 | |
| 268 | |
| 269 | /* |
| 270 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 271 | * producing a reduced-size 2x2 output block. |
| 272 | */ |
| 273 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 274 | GLOBAL(void) |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 275 | jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info *compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 276 | JCOEFPTR coef_block, |
| 277 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 278 | { |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 279 | JLONG tmp0, tmp10, z1; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 280 | JCOEFPTR inptr; |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 281 | ISLOW_MULT_TYPE *quantptr; |
| 282 | int *wsptr; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 283 | JSAMPROW outptr; |
| 284 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 285 | int ctr; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 286 | int workspace[DCTSIZE*2]; /* buffers data between passes */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 287 | SHIFT_TEMPS |
| 288 | |
| 289 | /* Pass 1: process columns from input, store into work array. */ |
| 290 | |
| 291 | inptr = coef_block; |
| 292 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 293 | wsptr = workspace; |
| 294 | for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { |
| 295 | /* Don't bother to process columns 2,4,6 */ |
| 296 | if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6) |
| 297 | continue; |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 298 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 299 | inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 300 | /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */ |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 301 | int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]), |
| 302 | PASS1_BITS); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 303 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 304 | wsptr[DCTSIZE*0] = dcval; |
| 305 | wsptr[DCTSIZE*1] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 306 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 307 | continue; |
| 308 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 309 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 310 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 311 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 312 | z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 313 | tmp10 = LEFT_SHIFT(z1, CONST_BITS+2); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 314 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 315 | /* Odd part */ |
| 316 | |
| 317 | z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); |
| 318 | tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */ |
| 319 | z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); |
| 320 | tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */ |
| 321 | z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); |
| 322 | tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */ |
| 323 | z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); |
| 324 | tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ |
| 325 | |
| 326 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 327 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 328 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2); |
| 329 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2); |
| 330 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 331 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 332 | /* Pass 2: process 2 rows from work array, store into output array. */ |
| 333 | |
| 334 | wsptr = workspace; |
| 335 | for (ctr = 0; ctr < 2; ctr++) { |
| 336 | outptr = output_buf[ctr] + output_col; |
| 337 | /* It's not clear whether a zero row test is worthwhile here ... */ |
| 338 | |
| 339 | #ifndef NO_ZERO_ROW_TEST |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 340 | if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 341 | /* AC terms all zero */ |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 342 | JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 343 | & RANGE_MASK]; |
| 344 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 345 | outptr[0] = dcval; |
| 346 | outptr[1] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 347 | |
| 348 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 349 | continue; |
| 350 | } |
| 351 | #endif |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 352 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 353 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 354 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 355 | tmp10 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+2); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 356 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 357 | /* Odd part */ |
| 358 | |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 359 | tmp0 = MULTIPLY((JLONG) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */ |
| 360 | + MULTIPLY((JLONG) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */ |
| 361 | + MULTIPLY((JLONG) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */ |
| 362 | + MULTIPLY((JLONG) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 363 | |
| 364 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 365 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 366 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 367 | CONST_BITS+PASS1_BITS+3+2) |
| 368 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 369 | outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 370 | CONST_BITS+PASS1_BITS+3+2) |
| 371 | & RANGE_MASK]; |
| 372 | |
| 373 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 374 | } |
| 375 | } |
| 376 | |
| 377 | |
| 378 | /* |
| 379 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 380 | * producing a reduced-size 1x1 output block. |
| 381 | */ |
| 382 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 383 | GLOBAL(void) |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 384 | jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info *compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 385 | JCOEFPTR coef_block, |
| 386 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 387 | { |
| 388 | int dcval; |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 389 | ISLOW_MULT_TYPE *quantptr; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 390 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 391 | SHIFT_TEMPS |
| 392 | |
| 393 | /* We hardly need an inverse DCT routine for this: just take the |
| 394 | * average pixel value, which is one-eighth of the DC coefficient. |
| 395 | */ |
| 396 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 397 | dcval = DEQUANTIZE(coef_block[0], quantptr[0]); |
Alex Naidis | 6eb7d37 | 2016-10-16 23:10:08 +0200 | [diff] [blame^] | 398 | dcval = (int) DESCALE((JLONG) dcval, 3); |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 399 | |
| 400 | output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; |
| 401 | } |
| 402 | |
| 403 | #endif /* IDCT_SCALING_SUPPORTED */ |