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annotate libs/libjpeg/jddctmgr.c @ 35:643f4ab609a4

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added readme and license
author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 31 Oct 2015 05:45:35 +0200
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nuclear@2 1 /*
nuclear@2 2 * jddctmgr.c
nuclear@2 3 *
nuclear@2 4 * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@2 5 * This file is part of the Independent JPEG Group's software.
nuclear@2 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@2 7 *
nuclear@2 8 * This file contains the inverse-DCT management logic.
nuclear@2 9 * This code selects a particular IDCT implementation to be used,
nuclear@2 10 * and it performs related housekeeping chores. No code in this file
nuclear@2 11 * is executed per IDCT step, only during output pass setup.
nuclear@2 12 *
nuclear@2 13 * Note that the IDCT routines are responsible for performing coefficient
nuclear@2 14 * dequantization as well as the IDCT proper. This module sets up the
nuclear@2 15 * dequantization multiplier table needed by the IDCT routine.
nuclear@2 16 */
nuclear@2 17
nuclear@2 18 #define JPEG_INTERNALS
nuclear@2 19 #include "jinclude.h"
nuclear@2 20 #include "jpeglib.h"
nuclear@2 21 #include "jdct.h" /* Private declarations for DCT subsystem */
nuclear@2 22
nuclear@2 23
nuclear@2 24 /*
nuclear@2 25 * The decompressor input side (jdinput.c) saves away the appropriate
nuclear@2 26 * quantization table for each component at the start of the first scan
nuclear@2 27 * involving that component. (This is necessary in order to correctly
nuclear@2 28 * decode files that reuse Q-table slots.)
nuclear@2 29 * When we are ready to make an output pass, the saved Q-table is converted
nuclear@2 30 * to a multiplier table that will actually be used by the IDCT routine.
nuclear@2 31 * The multiplier table contents are IDCT-method-dependent. To support
nuclear@2 32 * application changes in IDCT method between scans, we can remake the
nuclear@2 33 * multiplier tables if necessary.
nuclear@2 34 * In buffered-image mode, the first output pass may occur before any data
nuclear@2 35 * has been seen for some components, and thus before their Q-tables have
nuclear@2 36 * been saved away. To handle this case, multiplier tables are preset
nuclear@2 37 * to zeroes; the result of the IDCT will be a neutral gray level.
nuclear@2 38 */
nuclear@2 39
nuclear@2 40
nuclear@2 41 /* Private subobject for this module */
nuclear@2 42
nuclear@2 43 typedef struct {
nuclear@2 44 struct jpeg_inverse_dct pub; /* public fields */
nuclear@2 45
nuclear@2 46 /* This array contains the IDCT method code that each multiplier table
nuclear@2 47 * is currently set up for, or -1 if it's not yet set up.
nuclear@2 48 * The actual multiplier tables are pointed to by dct_table in the
nuclear@2 49 * per-component comp_info structures.
nuclear@2 50 */
nuclear@2 51 int cur_method[MAX_COMPONENTS];
nuclear@2 52 } my_idct_controller;
nuclear@2 53
nuclear@2 54 typedef my_idct_controller * my_idct_ptr;
nuclear@2 55
nuclear@2 56
nuclear@2 57 /* Allocated multiplier tables: big enough for any supported variant */
nuclear@2 58
nuclear@2 59 typedef union {
nuclear@2 60 ISLOW_MULT_TYPE islow_array[DCTSIZE2];
nuclear@2 61 #ifdef DCT_IFAST_SUPPORTED
nuclear@2 62 IFAST_MULT_TYPE ifast_array[DCTSIZE2];
nuclear@2 63 #endif
nuclear@2 64 #ifdef DCT_FLOAT_SUPPORTED
nuclear@2 65 FLOAT_MULT_TYPE float_array[DCTSIZE2];
nuclear@2 66 #endif
nuclear@2 67 } multiplier_table;
nuclear@2 68
nuclear@2 69
nuclear@2 70 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
nuclear@2 71 * so be sure to compile that code if either ISLOW or SCALING is requested.
nuclear@2 72 */
nuclear@2 73 #ifdef DCT_ISLOW_SUPPORTED
nuclear@2 74 #define PROVIDE_ISLOW_TABLES
nuclear@2 75 #else
nuclear@2 76 #ifdef IDCT_SCALING_SUPPORTED
nuclear@2 77 #define PROVIDE_ISLOW_TABLES
nuclear@2 78 #endif
nuclear@2 79 #endif
nuclear@2 80
nuclear@2 81
nuclear@2 82 /*
nuclear@2 83 * Prepare for an output pass.
nuclear@2 84 * Here we select the proper IDCT routine for each component and build
nuclear@2 85 * a matching multiplier table.
nuclear@2 86 */
nuclear@2 87
nuclear@2 88 METHODDEF(void)
nuclear@2 89 start_pass (j_decompress_ptr cinfo)
nuclear@2 90 {
nuclear@2 91 my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
nuclear@2 92 int ci, i;
nuclear@2 93 jpeg_component_info *compptr;
nuclear@2 94 int method = 0;
nuclear@2 95 inverse_DCT_method_ptr method_ptr = NULL;
nuclear@2 96 JQUANT_TBL * qtbl;
nuclear@2 97
nuclear@2 98 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@2 99 ci++, compptr++) {
nuclear@2 100 /* Select the proper IDCT routine for this component's scaling */
nuclear@2 101 switch (compptr->DCT_scaled_size) {
nuclear@2 102 #ifdef IDCT_SCALING_SUPPORTED
nuclear@2 103 case 1:
nuclear@2 104 method_ptr = jpeg_idct_1x1;
nuclear@2 105 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@2 106 break;
nuclear@2 107 case 2:
nuclear@2 108 method_ptr = jpeg_idct_2x2;
nuclear@2 109 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@2 110 break;
nuclear@2 111 case 4:
nuclear@2 112 method_ptr = jpeg_idct_4x4;
nuclear@2 113 method = JDCT_ISLOW; /* jidctred uses islow-style table */
nuclear@2 114 break;
nuclear@2 115 #endif
nuclear@2 116 case DCTSIZE:
nuclear@2 117 switch (cinfo->dct_method) {
nuclear@2 118 #ifdef DCT_ISLOW_SUPPORTED
nuclear@2 119 case JDCT_ISLOW:
nuclear@2 120 method_ptr = jpeg_idct_islow;
nuclear@2 121 method = JDCT_ISLOW;
nuclear@2 122 break;
nuclear@2 123 #endif
nuclear@2 124 #ifdef DCT_IFAST_SUPPORTED
nuclear@2 125 case JDCT_IFAST:
nuclear@2 126 method_ptr = jpeg_idct_ifast;
nuclear@2 127 method = JDCT_IFAST;
nuclear@2 128 break;
nuclear@2 129 #endif
nuclear@2 130 #ifdef DCT_FLOAT_SUPPORTED
nuclear@2 131 case JDCT_FLOAT:
nuclear@2 132 method_ptr = jpeg_idct_float;
nuclear@2 133 method = JDCT_FLOAT;
nuclear@2 134 break;
nuclear@2 135 #endif
nuclear@2 136 default:
nuclear@2 137 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@2 138 break;
nuclear@2 139 }
nuclear@2 140 break;
nuclear@2 141 default:
nuclear@2 142 ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
nuclear@2 143 break;
nuclear@2 144 }
nuclear@2 145 idct->pub.inverse_DCT[ci] = method_ptr;
nuclear@2 146 /* Create multiplier table from quant table.
nuclear@2 147 * However, we can skip this if the component is uninteresting
nuclear@2 148 * or if we already built the table. Also, if no quant table
nuclear@2 149 * has yet been saved for the component, we leave the
nuclear@2 150 * multiplier table all-zero; we'll be reading zeroes from the
nuclear@2 151 * coefficient controller's buffer anyway.
nuclear@2 152 */
nuclear@2 153 if (! compptr->component_needed || idct->cur_method[ci] == method)
nuclear@2 154 continue;
nuclear@2 155 qtbl = compptr->quant_table;
nuclear@2 156 if (qtbl == NULL) /* happens if no data yet for component */
nuclear@2 157 continue;
nuclear@2 158 idct->cur_method[ci] = method;
nuclear@2 159 switch (method) {
nuclear@2 160 #ifdef PROVIDE_ISLOW_TABLES
nuclear@2 161 case JDCT_ISLOW:
nuclear@2 162 {
nuclear@2 163 /* For LL&M IDCT method, multipliers are equal to raw quantization
nuclear@2 164 * coefficients, but are stored as ints to ensure access efficiency.
nuclear@2 165 */
nuclear@2 166 ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
nuclear@2 167 for (i = 0; i < DCTSIZE2; i++) {
nuclear@2 168 ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
nuclear@2 169 }
nuclear@2 170 }
nuclear@2 171 break;
nuclear@2 172 #endif
nuclear@2 173 #ifdef DCT_IFAST_SUPPORTED
nuclear@2 174 case JDCT_IFAST:
nuclear@2 175 {
nuclear@2 176 /* For AA&N IDCT method, multipliers are equal to quantization
nuclear@2 177 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@2 178 * scalefactor[0] = 1
nuclear@2 179 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
nuclear@2 180 * For integer operation, the multiplier table is to be scaled by
nuclear@2 181 * IFAST_SCALE_BITS.
nuclear@2 182 */
nuclear@2 183 IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
nuclear@2 184 #define CONST_BITS 14
nuclear@2 185 static const INT16 aanscales[DCTSIZE2] = {
nuclear@2 186 /* precomputed values scaled up by 14 bits */
nuclear@2 187 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
nuclear@2 188 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
nuclear@2 189 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
nuclear@2 190 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
nuclear@2 191 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
nuclear@2 192 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
nuclear@2 193 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
nuclear@2 194 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
nuclear@2 195 };
nuclear@2 196 SHIFT_TEMPS
nuclear@2 197
nuclear@2 198 for (i = 0; i < DCTSIZE2; i++) {
nuclear@2 199 ifmtbl[i] = (IFAST_MULT_TYPE)
nuclear@2 200 DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
nuclear@2 201 (INT32) aanscales[i]),
nuclear@2 202 CONST_BITS-IFAST_SCALE_BITS);
nuclear@2 203 }
nuclear@2 204 }
nuclear@2 205 break;
nuclear@2 206 #endif
nuclear@2 207 #ifdef DCT_FLOAT_SUPPORTED
nuclear@2 208 case JDCT_FLOAT:
nuclear@2 209 {
nuclear@2 210 /* For float AA&N IDCT method, multipliers are equal to quantization
nuclear@2 211 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@2 212 * scalefactor[0] = 1
nuclear@2 213 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
nuclear@2 214 */
nuclear@2 215 FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
nuclear@2 216 int row, col;
nuclear@2 217 static const double aanscalefactor[DCTSIZE] = {
nuclear@2 218 1.0, 1.387039845, 1.306562965, 1.175875602,
nuclear@2 219 1.0, 0.785694958, 0.541196100, 0.275899379
nuclear@2 220 };
nuclear@2 221
nuclear@2 222 i = 0;
nuclear@2 223 for (row = 0; row < DCTSIZE; row++) {
nuclear@2 224 for (col = 0; col < DCTSIZE; col++) {
nuclear@2 225 fmtbl[i] = (FLOAT_MULT_TYPE)
nuclear@2 226 ((double) qtbl->quantval[i] *
nuclear@2 227 aanscalefactor[row] * aanscalefactor[col]);
nuclear@2 228 i++;
nuclear@2 229 }
nuclear@2 230 }
nuclear@2 231 }
nuclear@2 232 break;
nuclear@2 233 #endif
nuclear@2 234 default:
nuclear@2 235 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@2 236 break;
nuclear@2 237 }
nuclear@2 238 }
nuclear@2 239 }
nuclear@2 240
nuclear@2 241
nuclear@2 242 /*
nuclear@2 243 * Initialize IDCT manager.
nuclear@2 244 */
nuclear@2 245
nuclear@2 246 GLOBAL(void)
nuclear@2 247 jinit_inverse_dct (j_decompress_ptr cinfo)
nuclear@2 248 {
nuclear@2 249 my_idct_ptr idct;
nuclear@2 250 int ci;
nuclear@2 251 jpeg_component_info *compptr;
nuclear@2 252
nuclear@2 253 idct = (my_idct_ptr)
nuclear@2 254 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2 255 SIZEOF(my_idct_controller));
nuclear@2 256 cinfo->idct = (struct jpeg_inverse_dct *) idct;
nuclear@2 257 idct->pub.start_pass = start_pass;
nuclear@2 258
nuclear@2 259 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@2 260 ci++, compptr++) {
nuclear@2 261 /* Allocate and pre-zero a multiplier table for each component */
nuclear@2 262 compptr->dct_table =
nuclear@2 263 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2 264 SIZEOF(multiplier_table));
nuclear@2 265 MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
nuclear@2 266 /* Mark multiplier table not yet set up for any method */
nuclear@2 267 idct->cur_method[ci] = -1;
nuclear@2 268 }
nuclear@2 269 }