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: |
| 7 | * Copyright (C) 2015, D. R. Commander |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 8 | * For conditions of distribution and use, see the accompanying README file. |
| 9 | * |
| 10 | * This file contains inverse-DCT routines that produce reduced-size output: |
| 11 | * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block. |
| 12 | * |
| 13 | * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M) |
| 14 | * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step |
| 15 | * with an 8-to-4 step that produces the four averages of two adjacent outputs |
| 16 | * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output). |
| 17 | * These steps were derived by computing the corresponding values at the end |
| 18 | * of the normal LL&M code, then simplifying as much as possible. |
| 19 | * |
| 20 | * 1x1 is trivial: just take the DC coefficient divided by 8. |
| 21 | * |
| 22 | * See jidctint.c for additional comments. |
| 23 | */ |
| 24 | |
| 25 | #define JPEG_INTERNALS |
| 26 | #include "jinclude.h" |
| 27 | #include "jpeglib.h" |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 28 | #include "jdct.h" /* Private declarations for DCT subsystem */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 29 | |
| 30 | #ifdef IDCT_SCALING_SUPPORTED |
| 31 | |
| 32 | |
| 33 | /* |
| 34 | * This module is specialized to the case DCTSIZE = 8. |
| 35 | */ |
| 36 | |
| 37 | #if DCTSIZE != 8 |
| 38 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
| 39 | #endif |
| 40 | |
| 41 | |
| 42 | /* Scaling is the same as in jidctint.c. */ |
| 43 | |
| 44 | #if BITS_IN_JSAMPLE == 8 |
| 45 | #define CONST_BITS 13 |
| 46 | #define PASS1_BITS 2 |
| 47 | #else |
| 48 | #define CONST_BITS 13 |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 49 | #define PASS1_BITS 1 /* lose a little precision to avoid overflow */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 50 | #endif |
| 51 | |
| 52 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
| 53 | * causing a lot of useless floating-point operations at run time. |
| 54 | * To get around this we use the following pre-calculated constants. |
| 55 | * If you change CONST_BITS you may want to add appropriate values. |
| 56 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
| 57 | */ |
| 58 | |
| 59 | #if CONST_BITS == 13 |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 60 | #define FIX_0_211164243 ((INT32) 1730) /* FIX(0.211164243) */ |
| 61 | #define FIX_0_509795579 ((INT32) 4176) /* FIX(0.509795579) */ |
| 62 | #define FIX_0_601344887 ((INT32) 4926) /* FIX(0.601344887) */ |
| 63 | #define FIX_0_720959822 ((INT32) 5906) /* FIX(0.720959822) */ |
| 64 | #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */ |
| 65 | #define FIX_0_850430095 ((INT32) 6967) /* FIX(0.850430095) */ |
| 66 | #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */ |
| 67 | #define FIX_1_061594337 ((INT32) 8697) /* FIX(1.061594337) */ |
| 68 | #define FIX_1_272758580 ((INT32) 10426) /* FIX(1.272758580) */ |
| 69 | #define FIX_1_451774981 ((INT32) 11893) /* FIX(1.451774981) */ |
| 70 | #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */ |
| 71 | #define FIX_2_172734803 ((INT32) 17799) /* FIX(2.172734803) */ |
| 72 | #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */ |
| 73 | #define FIX_3_624509785 ((INT32) 29692) /* FIX(3.624509785) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 74 | #else |
| 75 | #define FIX_0_211164243 FIX(0.211164243) |
| 76 | #define FIX_0_509795579 FIX(0.509795579) |
| 77 | #define FIX_0_601344887 FIX(0.601344887) |
| 78 | #define FIX_0_720959822 FIX(0.720959822) |
| 79 | #define FIX_0_765366865 FIX(0.765366865) |
| 80 | #define FIX_0_850430095 FIX(0.850430095) |
| 81 | #define FIX_0_899976223 FIX(0.899976223) |
| 82 | #define FIX_1_061594337 FIX(1.061594337) |
| 83 | #define FIX_1_272758580 FIX(1.272758580) |
| 84 | #define FIX_1_451774981 FIX(1.451774981) |
| 85 | #define FIX_1_847759065 FIX(1.847759065) |
| 86 | #define FIX_2_172734803 FIX(2.172734803) |
| 87 | #define FIX_2_562915447 FIX(2.562915447) |
| 88 | #define FIX_3_624509785 FIX(3.624509785) |
| 89 | #endif |
| 90 | |
| 91 | |
| 92 | /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. |
| 93 | * For 8-bit samples with the recommended scaling, all the variable |
| 94 | * and constant values involved are no more than 16 bits wide, so a |
| 95 | * 16x16->32 bit multiply can be used instead of a full 32x32 multiply. |
| 96 | * For 12-bit samples, a full 32-bit multiplication will be needed. |
| 97 | */ |
| 98 | |
| 99 | #if BITS_IN_JSAMPLE == 8 |
| 100 | #define MULTIPLY(var,const) MULTIPLY16C16(var,const) |
| 101 | #else |
| 102 | #define MULTIPLY(var,const) ((var) * (const)) |
| 103 | #endif |
| 104 | |
| 105 | |
| 106 | /* Dequantize a coefficient by multiplying it by the multiplier-table |
| 107 | * entry; produce an int result. In this module, both inputs and result |
| 108 | * are 16 bits or less, so either int or short multiply will work. |
| 109 | */ |
| 110 | |
| 111 | #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) |
| 112 | |
| 113 | |
| 114 | /* |
| 115 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 116 | * producing a reduced-size 4x4 output block. |
| 117 | */ |
| 118 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 119 | GLOBAL(void) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 120 | jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 121 | JCOEFPTR coef_block, |
| 122 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 123 | { |
| 124 | INT32 tmp0, tmp2, tmp10, tmp12; |
| 125 | INT32 z1, z2, z3, z4; |
| 126 | JCOEFPTR inptr; |
| 127 | ISLOW_MULT_TYPE * quantptr; |
| 128 | int * wsptr; |
| 129 | JSAMPROW outptr; |
| 130 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 131 | int ctr; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 132 | int workspace[DCTSIZE*4]; /* buffers data between passes */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 133 | SHIFT_TEMPS |
| 134 | |
| 135 | /* Pass 1: process columns from input, store into work array. */ |
| 136 | |
| 137 | inptr = coef_block; |
| 138 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 139 | wsptr = workspace; |
| 140 | for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { |
| 141 | /* Don't bother to process column 4, because second pass won't use it */ |
| 142 | if (ctr == DCTSIZE-4) |
| 143 | continue; |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 144 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 145 | inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 && |
| 146 | inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 147 | /* AC terms all zero; we need not examine term 4 for 4x4 output */ |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 148 | int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]), |
| 149 | PASS1_BITS); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 150 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 151 | wsptr[DCTSIZE*0] = dcval; |
| 152 | wsptr[DCTSIZE*1] = dcval; |
| 153 | wsptr[DCTSIZE*2] = dcval; |
| 154 | wsptr[DCTSIZE*3] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 155 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 156 | continue; |
| 157 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 158 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 159 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 160 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 161 | tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 162 | tmp0 = LEFT_SHIFT(tmp0, CONST_BITS+1); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 163 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 164 | z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); |
| 165 | z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); |
| 166 | |
| 167 | tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 168 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 169 | tmp10 = tmp0 + tmp2; |
| 170 | tmp12 = tmp0 - tmp2; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 171 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 172 | /* Odd part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 173 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 174 | z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); |
| 175 | z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); |
| 176 | z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); |
| 177 | z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 178 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 179 | tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 180 | + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ |
| 181 | + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ |
| 182 | + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ |
| 183 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 184 | tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 185 | + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ |
| 186 | + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ |
| 187 | + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 188 | |
| 189 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 190 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 191 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); |
| 192 | wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); |
| 193 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); |
| 194 | wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); |
| 195 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 196 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 197 | /* Pass 2: process 4 rows from work array, store into output array. */ |
| 198 | |
| 199 | wsptr = workspace; |
| 200 | for (ctr = 0; ctr < 4; ctr++) { |
| 201 | outptr = output_buf[ctr] + output_col; |
| 202 | /* It's not clear whether a zero row test is worthwhile here ... */ |
| 203 | |
| 204 | #ifndef NO_ZERO_ROW_TEST |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 205 | if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 206 | wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 207 | /* AC terms all zero */ |
| 208 | JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 209 | & RANGE_MASK]; |
| 210 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 211 | outptr[0] = dcval; |
| 212 | outptr[1] = dcval; |
| 213 | outptr[2] = dcval; |
| 214 | outptr[3] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 215 | |
| 216 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 217 | continue; |
| 218 | } |
| 219 | #endif |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 220 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 221 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 222 | |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 223 | tmp0 = LEFT_SHIFT((INT32) wsptr[0], CONST_BITS+1); |
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 | tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 226 | + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865); |
| 227 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 228 | tmp10 = tmp0 + tmp2; |
| 229 | tmp12 = tmp0 - tmp2; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 230 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 231 | /* Odd part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 232 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 233 | z1 = (INT32) wsptr[7]; |
| 234 | z2 = (INT32) wsptr[5]; |
| 235 | z3 = (INT32) wsptr[3]; |
| 236 | z4 = (INT32) wsptr[1]; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 237 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 238 | tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 239 | + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ |
| 240 | + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ |
| 241 | + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ |
| 242 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 243 | tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 244 | + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ |
| 245 | + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ |
| 246 | + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 247 | |
| 248 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 249 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 250 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 251 | CONST_BITS+PASS1_BITS+3+1) |
| 252 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 253 | outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 254 | CONST_BITS+PASS1_BITS+3+1) |
| 255 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 256 | outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 257 | CONST_BITS+PASS1_BITS+3+1) |
| 258 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 259 | outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 260 | CONST_BITS+PASS1_BITS+3+1) |
| 261 | & RANGE_MASK]; |
| 262 | |
| 263 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 264 | } |
| 265 | } |
| 266 | |
| 267 | |
| 268 | /* |
| 269 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 270 | * producing a reduced-size 2x2 output block. |
| 271 | */ |
| 272 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 273 | GLOBAL(void) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 274 | jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 275 | JCOEFPTR coef_block, |
| 276 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 277 | { |
| 278 | INT32 tmp0, tmp10, z1; |
| 279 | JCOEFPTR inptr; |
| 280 | ISLOW_MULT_TYPE * quantptr; |
| 281 | int * wsptr; |
| 282 | JSAMPROW outptr; |
| 283 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 284 | int ctr; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 285 | int workspace[DCTSIZE*2]; /* buffers data between passes */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 286 | SHIFT_TEMPS |
| 287 | |
| 288 | /* Pass 1: process columns from input, store into work array. */ |
| 289 | |
| 290 | inptr = coef_block; |
| 291 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 292 | wsptr = workspace; |
| 293 | for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { |
| 294 | /* Don't bother to process columns 2,4,6 */ |
| 295 | if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6) |
| 296 | continue; |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 297 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 && |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 298 | inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) { |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 299 | /* 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] | 300 | int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]), |
| 301 | PASS1_BITS); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 302 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 303 | wsptr[DCTSIZE*0] = dcval; |
| 304 | wsptr[DCTSIZE*1] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 305 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 306 | continue; |
| 307 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 308 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 309 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 310 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 311 | z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 312 | tmp10 = LEFT_SHIFT(z1, CONST_BITS+2); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 313 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 314 | /* Odd part */ |
| 315 | |
| 316 | z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); |
| 317 | tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */ |
| 318 | z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); |
| 319 | tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */ |
| 320 | z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); |
| 321 | tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */ |
| 322 | z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); |
| 323 | tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ |
| 324 | |
| 325 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 326 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 327 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2); |
| 328 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2); |
| 329 | } |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 330 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 331 | /* Pass 2: process 2 rows from work array, store into output array. */ |
| 332 | |
| 333 | wsptr = workspace; |
| 334 | for (ctr = 0; ctr < 2; ctr++) { |
| 335 | outptr = output_buf[ctr] + output_col; |
| 336 | /* It's not clear whether a zero row test is worthwhile here ... */ |
| 337 | |
| 338 | #ifndef NO_ZERO_ROW_TEST |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 339 | 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] | 340 | /* AC terms all zero */ |
| 341 | JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 342 | & RANGE_MASK]; |
| 343 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 344 | outptr[0] = dcval; |
| 345 | outptr[1] = dcval; |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 346 | |
| 347 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 348 | continue; |
| 349 | } |
| 350 | #endif |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 351 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 352 | /* Even part */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 353 | |
DRC | 8e9cef2 | 2015-09-21 12:57:41 -0500 | [diff] [blame] | 354 | tmp10 = LEFT_SHIFT((INT32) wsptr[0], CONST_BITS+2); |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 355 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 356 | /* Odd part */ |
| 357 | |
| 358 | tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 359 | + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */ |
| 360 | + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */ |
| 361 | + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 362 | |
| 363 | /* Final output stage */ |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 364 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 365 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 366 | CONST_BITS+PASS1_BITS+3+2) |
| 367 | & RANGE_MASK]; |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 368 | outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 369 | CONST_BITS+PASS1_BITS+3+2) |
| 370 | & RANGE_MASK]; |
| 371 | |
| 372 | wsptr += DCTSIZE; /* advance pointer to next row */ |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 373 | } |
| 374 | } |
| 375 | |
| 376 | |
| 377 | /* |
| 378 | * Perform dequantization and inverse DCT on one block of coefficients, |
| 379 | * producing a reduced-size 1x1 output block. |
| 380 | */ |
| 381 | |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 382 | GLOBAL(void) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 383 | jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr, |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 384 | JCOEFPTR coef_block, |
| 385 | JSAMPARRAY output_buf, JDIMENSION output_col) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 386 | { |
| 387 | int dcval; |
| 388 | ISLOW_MULT_TYPE * quantptr; |
| 389 | JSAMPLE *range_limit = IDCT_range_limit(cinfo); |
| 390 | SHIFT_TEMPS |
| 391 | |
| 392 | /* We hardly need an inverse DCT routine for this: just take the |
| 393 | * average pixel value, which is one-eighth of the DC coefficient. |
| 394 | */ |
| 395 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; |
| 396 | dcval = DEQUANTIZE(coef_block[0], quantptr[0]); |
| 397 | dcval = (int) DESCALE((INT32) dcval, 3); |
| 398 | |
| 399 | output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; |
| 400 | } |
| 401 | |
| 402 | #endif /* IDCT_SCALING_SUPPORTED */ |