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annotate libs/libjpeg/jddctmgr.c @ 0:b2f14e535253

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author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 01 Feb 2014 19:58:19 +0200
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nuclear@0 1 /*
nuclear@0 2 * jddctmgr.c
nuclear@0 3 *
nuclear@0 4 * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@0 5 * This file is part of the Independent JPEG Group's software.
nuclear@0 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@0 7 *
nuclear@0 8 * This file contains the inverse-DCT management logic.
nuclear@0 9 * This code selects a particular IDCT implementation to be used,
nuclear@0 10 * and it performs related housekeeping chores. No code in this file
nuclear@0 11 * is executed per IDCT step, only during output pass setup.
nuclear@0 12 *
nuclear@0 13 * Note that the IDCT routines are responsible for performing coefficient
nuclear@0 14 * dequantization as well as the IDCT proper. This module sets up the
nuclear@0 15 * dequantization multiplier table needed by the IDCT routine.
nuclear@0 16 */
nuclear@0 17
nuclear@0 18 #define JPEG_INTERNALS
nuclear@0 19 #include "jinclude.h"
nuclear@0 20 #include "jpeglib.h"
nuclear@0 21 #include "jdct.h" /* Private declarations for DCT subsystem */
nuclear@0 22
nuclear@0 23
nuclear@0 24 /*
nuclear@0 25 * The decompressor input side (jdinput.c) saves away the appropriate
nuclear@0 26 * quantization table for each component at the start of the first scan
nuclear@0 27 * involving that component. (This is necessary in order to correctly
nuclear@0 28 * decode files that reuse Q-table slots.)
nuclear@0 29 * When we are ready to make an output pass, the saved Q-table is converted
nuclear@0 30 * to a multiplier table that will actually be used by the IDCT routine.
nuclear@0 31 * The multiplier table contents are IDCT-method-dependent. To support
nuclear@0 32 * application changes in IDCT method between scans, we can remake the
nuclear@0 33 * multiplier tables if necessary.
nuclear@0 34 * In buffered-image mode, the first output pass may occur before any data
nuclear@0 35 * has been seen for some components, and thus before their Q-tables have
nuclear@0 36 * been saved away. To handle this case, multiplier tables are preset
nuclear@0 37 * to zeroes; the result of the IDCT will be a neutral gray level.
nuclear@0 38 */
nuclear@0 39
nuclear@0 40
nuclear@0 41 /* Private subobject for this module */
nuclear@0 42
nuclear@0 43 typedef struct {
nuclear@0 44 struct jpeg_inverse_dct pub; /* public fields */
nuclear@0 45
nuclear@0 46 /* This array contains the IDCT method code that each multiplier table
nuclear@0 47 * is currently set up for, or -1 if it's not yet set up.
nuclear@0 48 * The actual multiplier tables are pointed to by dct_table in the
nuclear@0 49 * per-component comp_info structures.
nuclear@0 50 */
nuclear@0 51 int cur_method[MAX_COMPONENTS];
nuclear@0 52 } my_idct_controller;
nuclear@0 53
nuclear@0 54 typedef my_idct_controller * my_idct_ptr;
nuclear@0 55
nuclear@0 56
nuclear@0 57 /* Allocated multiplier tables: big enough for any supported variant */
nuclear@0 58
nuclear@0 59 typedef union {
nuclear@0 60 ISLOW_MULT_TYPE islow_array[DCTSIZE2];
nuclear@0 61 #ifdef DCT_IFAST_SUPPORTED
nuclear@0 62 IFAST_MULT_TYPE ifast_array[DCTSIZE2];
nuclear@0 63 #endif
nuclear@0 64 #ifdef DCT_FLOAT_SUPPORTED
nuclear@0 65 FLOAT_MULT_TYPE float_array[DCTSIZE2];
nuclear@0 66 #endif
nuclear@0 67 } multiplier_table;
nuclear@0 68
nuclear@0 69
nuclear@0 70 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
nuclear@0 71 * so be sure to compile that code if either ISLOW or SCALING is requested.
nuclear@0 72 */
nuclear@0 73 #ifdef DCT_ISLOW_SUPPORTED
nuclear@0 74 #define PROVIDE_ISLOW_TABLES
nuclear@0 75 #else
nuclear@0 76 #ifdef IDCT_SCALING_SUPPORTED
nuclear@0 77 #define PROVIDE_ISLOW_TABLES
nuclear@0 78 #endif
nuclear@0 79 #endif
nuclear@0 80
nuclear@0 81
nuclear@0 82 /*
nuclear@0 83 * Prepare for an output pass.
nuclear@0 84 * Here we select the proper IDCT routine for each component and build
nuclear@0 85 * a matching multiplier table.
nuclear@0 86 */
nuclear@0 87
nuclear@0 88 METHODDEF(void)
nuclear@0 89 start_pass (j_decompress_ptr cinfo)
nuclear@0 90 {
nuclear@0 91 my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
nuclear@0 92 int ci, i;
nuclear@0 93 jpeg_component_info *compptr;
nuclear@0 94 int method = 0;
nuclear@0 95 inverse_DCT_method_ptr method_ptr = NULL;
nuclear@0 96 JQUANT_TBL * qtbl;
nuclear@0 97
nuclear@0 98 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@0 99 ci++, compptr++) {
nuclear@0 100 /* Select the proper IDCT routine for this component's scaling */
nuclear@0 101 switch (compptr->DCT_scaled_size) {
nuclear@0 102 #ifdef IDCT_SCALING_SUPPORTED
nuclear@0 103 case 1:
nuclear@0 104 method_ptr = jpeg_idct_1x1;
nuclear@0 105 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@0 106 break;
nuclear@0 107 case 2:
nuclear@0 108 method_ptr = jpeg_idct_2x2;
nuclear@0 109 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@0 110 break;
nuclear@0 111 case 4:
nuclear@0 112 method_ptr = jpeg_idct_4x4;
nuclear@0 113 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@0 114 break;
nuclear@0 115 #endif
nuclear@0 116 case DCTSIZE:
nuclear@0 117 switch (cinfo->dct_method) {
nuclear@0 118 #ifdef DCT_ISLOW_SUPPORTED
nuclear@0 119 case JDCT_ISLOW:
nuclear@0 120 method_ptr = jpeg_idct_islow;
nuclear@0 121 method = JDCT_ISLOW;
nuclear@0 122 break;
nuclear@0 123 #endif
nuclear@0 124 #ifdef DCT_IFAST_SUPPORTED
nuclear@0 125 case JDCT_IFAST:
nuclear@0 126 method_ptr = jpeg_idct_ifast;
nuclear@0 127 method = JDCT_IFAST;
nuclear@0 128 break;
nuclear@0 129 #endif
nuclear@0 130 #ifdef DCT_FLOAT_SUPPORTED
nuclear@0 131 case JDCT_FLOAT:
nuclear@0 132 method_ptr = jpeg_idct_float;
nuclear@0 133 method = JDCT_FLOAT;
nuclear@0 134 break;
nuclear@0 135 #endif
nuclear@0 136 default:
nuclear@0 137 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@0 138 break;
nuclear@0 139 }
nuclear@0 140 break;
nuclear@0 141 default:
nuclear@0 142 ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
nuclear@0 143 break;
nuclear@0 144 }
nuclear@0 145 idct->pub.inverse_DCT[ci] = method_ptr;
nuclear@0 146 /* Create multiplier table from quant table.
nuclear@0 147 * However, we can skip this if the component is uninteresting
nuclear@0 148 * or if we already built the table. Also, if no quant table
nuclear@0 149 * has yet been saved for the component, we leave the
nuclear@0 150 * multiplier table all-zero; we'll be reading zeroes from the
nuclear@0 151 * coefficient controller's buffer anyway.
nuclear@0 152 */
nuclear@0 153 if (! compptr->component_needed || idct->cur_method[ci] == method)
nuclear@0 154 continue;
nuclear@0 155 qtbl = compptr->quant_table;
nuclear@0 156 if (qtbl == NULL) /* happens if no data yet for component */
nuclear@0 157 continue;
nuclear@0 158 idct->cur_method[ci] = method;
nuclear@0 159 switch (method) {
nuclear@0 160 #ifdef PROVIDE_ISLOW_TABLES
nuclear@0 161 case JDCT_ISLOW:
nuclear@0 162 {
nuclear@0 163 /* For LL&M IDCT method, multipliers are equal to raw quantization
nuclear@0 164 * coefficients, but are stored as ints to ensure access efficiency.
nuclear@0 165 */
nuclear@0 166 ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
nuclear@0 167 for (i = 0; i < DCTSIZE2; i++) {
nuclear@0 168 ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
nuclear@0 169 }
nuclear@0 170 }
nuclear@0 171 break;
nuclear@0 172 #endif
nuclear@0 173 #ifdef DCT_IFAST_SUPPORTED
nuclear@0 174 case JDCT_IFAST:
nuclear@0 175 {
nuclear@0 176 /* For AA&N IDCT method, multipliers are equal to quantization
nuclear@0 177 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@0 178 * scalefactor[0] = 1
nuclear@0 179 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
nuclear@0 180 * For integer operation, the multiplier table is to be scaled by
nuclear@0 181 * IFAST_SCALE_BITS.
nuclear@0 182 */
nuclear@0 183 IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
nuclear@0 184 #define CONST_BITS 14
nuclear@0 185 static const INT16 aanscales[DCTSIZE2] = {
nuclear@0 186 /* precomputed values scaled up by 14 bits */
nuclear@0 187 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
nuclear@0 188 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
nuclear@0 189 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
nuclear@0 190 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
nuclear@0 191 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
nuclear@0 192 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
nuclear@0 193 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
nuclear@0 194 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
nuclear@0 195 };
nuclear@0 196 SHIFT_TEMPS
nuclear@0 197
nuclear@0 198 for (i = 0; i < DCTSIZE2; i++) {
nuclear@0 199 ifmtbl[i] = (IFAST_MULT_TYPE)
nuclear@0 200 DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
nuclear@0 201 (INT32) aanscales[i]),
nuclear@0 202 CONST_BITS-IFAST_SCALE_BITS);
nuclear@0 203 }
nuclear@0 204 }
nuclear@0 205 break;
nuclear@0 206 #endif
nuclear@0 207 #ifdef DCT_FLOAT_SUPPORTED
nuclear@0 208 case JDCT_FLOAT:
nuclear@0 209 {
nuclear@0 210 /* For float AA&N IDCT method, multipliers are equal to quantization
nuclear@0 211 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@0 212 * scalefactor[0] = 1
nuclear@0 213 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
nuclear@0 214 */
nuclear@0 215 FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
nuclear@0 216 int row, col;
nuclear@0 217 static const double aanscalefactor[DCTSIZE] = {
nuclear@0 218 1.0, 1.387039845, 1.306562965, 1.175875602,
nuclear@0 219 1.0, 0.785694958, 0.541196100, 0.275899379
nuclear@0 220 };
nuclear@0 221
nuclear@0 222 i = 0;
nuclear@0 223 for (row = 0; row < DCTSIZE; row++) {
nuclear@0 224 for (col = 0; col < DCTSIZE; col++) {
nuclear@0 225 fmtbl[i] = (FLOAT_MULT_TYPE)
nuclear@0 226 ((double) qtbl->quantval[i] *
nuclear@0 227 aanscalefactor[row] * aanscalefactor[col]);
nuclear@0 228 i++;
nuclear@0 229 }
nuclear@0 230 }
nuclear@0 231 }
nuclear@0 232 break;
nuclear@0 233 #endif
nuclear@0 234 default:
nuclear@0 235 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@0 236 break;
nuclear@0 237 }
nuclear@0 238 }
nuclear@0 239 }
nuclear@0 240
nuclear@0 241
nuclear@0 242 /*
nuclear@0 243 * Initialize IDCT manager.
nuclear@0 244 */
nuclear@0 245
nuclear@0 246 GLOBAL(void)
nuclear@0 247 jinit_inverse_dct (j_decompress_ptr cinfo)
nuclear@0 248 {
nuclear@0 249 my_idct_ptr idct;
nuclear@0 250 int ci;
nuclear@0 251 jpeg_component_info *compptr;
nuclear@0 252
nuclear@0 253 idct = (my_idct_ptr)
nuclear@0 254 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 255 SIZEOF(my_idct_controller));
nuclear@0 256 cinfo->idct = (struct jpeg_inverse_dct *) idct;
nuclear@0 257 idct->pub.start_pass = start_pass;
nuclear@0 258
nuclear@0 259 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@0 260 ci++, compptr++) {
nuclear@0 261 /* Allocate and pre-zero a multiplier table for each component */
nuclear@0 262 compptr->dct_table =
nuclear@0 263 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 264 SIZEOF(multiplier_table));
nuclear@0 265 MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
nuclear@0 266 /* Mark multiplier table not yet set up for any method */
nuclear@0 267 idct->cur_method[ci] = -1;
nuclear@0 268 }
nuclear@0 269 }