1 #if !defined(_FX_JPEG_TURBO_) 2 /* 3 * jddctmgr.c 4 * 5 * Copyright (C) 1994-1996, Thomas G. Lane. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains the inverse-DCT management logic. 10 * This code selects a particular IDCT implementation to be used, 11 * and it performs related housekeeping chores. No code in this file 12 * is executed per IDCT step, only during output pass setup. 13 * 14 * Note that the IDCT routines are responsible for performing coefficient 15 * dequantization as well as the IDCT proper. This module sets up the 16 * dequantization multiplier table needed by the IDCT routine. 17 */ 18 19 #define JPEG_INTERNALS 20 #include "jinclude.h" 21 #include "jpeglib.h" 22 #include "jdct.h" /* Private declarations for DCT subsystem */ 23 24 25 /* 26 * The decompressor input side (jdinput.c) saves away the appropriate 27 * quantization table for each component at the start of the first scan 28 * involving that component. (This is necessary in order to correctly 29 * decode files that reuse Q-table slots.) 30 * When we are ready to make an output pass, the saved Q-table is converted 31 * to a multiplier table that will actually be used by the IDCT routine. 32 * The multiplier table contents are IDCT-method-dependent. To support 33 * application changes in IDCT method between scans, we can remake the 34 * multiplier tables if necessary. 35 * In buffered-image mode, the first output pass may occur before any data 36 * has been seen for some components, and thus before their Q-tables have 37 * been saved away. To handle this case, multiplier tables are preset 38 * to zeroes; the result of the IDCT will be a neutral gray level. 39 */ 40 41 42 /* Private subobject for this module */ 43 44 typedef struct { 45 struct jpeg_inverse_dct pub; /* public fields */ 46 47 /* This array contains the IDCT method code that each multiplier table 48 * is currently set up for, or -1 if it's not yet set up. 49 * The actual multiplier tables are pointed to by dct_table in the 50 * per-component comp_info structures. 51 */ 52 int cur_method[MAX_COMPONENTS]; 53 } my_idct_controller; 54 55 typedef my_idct_controller * my_idct_ptr; 56 57 58 /* Allocated multiplier tables: big enough for any supported variant */ 59 60 typedef union { 61 ISLOW_MULT_TYPE islow_array[DCTSIZE2]; 62 #ifdef DCT_IFAST_SUPPORTED 63 IFAST_MULT_TYPE ifast_array[DCTSIZE2]; 64 #endif 65 #ifdef DCT_FLOAT_SUPPORTED 66 FLOAT_MULT_TYPE float_array[DCTSIZE2]; 67 #endif 68 } multiplier_table; 69 70 71 /* The current scaled-IDCT routines require ISLOW-style multiplier tables, 72 * so be sure to compile that code if either ISLOW or SCALING is requested. 73 */ 74 #ifdef DCT_ISLOW_SUPPORTED 75 #define PROVIDE_ISLOW_TABLES 76 #else 77 #ifdef IDCT_SCALING_SUPPORTED 78 #define PROVIDE_ISLOW_TABLES 79 #endif 80 #endif 81 82 83 /* 84 * Prepare for an output pass. 85 * Here we select the proper IDCT routine for each component and build 86 * a matching multiplier table. 87 */ 88 89 METHODDEF(void) 90 start_pass (j_decompress_ptr cinfo) 91 { 92 my_idct_ptr idct = (my_idct_ptr) cinfo->idct; 93 int ci, i; 94 jpeg_component_info *compptr; 95 int method = 0; 96 inverse_DCT_method_ptr method_ptr = NULL; 97 JQUANT_TBL * qtbl; 98 99 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 100 ci++, compptr++) { 101 /* Select the proper IDCT routine for this component's scaling */ 102 switch (compptr->DCT_scaled_size) { 103 #ifdef IDCT_SCALING_SUPPORTED 104 case 1: 105 method_ptr = jpeg_idct_1x1; 106 method = JDCT_ISLOW; /* jidctred uses islow-style table */ 107 break; 108 case 2: 109 method_ptr = jpeg_idct_2x2; 110 method = JDCT_ISLOW; /* jidctred uses islow-style table */ 111 break; 112 case 4: 113 method_ptr = jpeg_idct_4x4; 114 method = JDCT_ISLOW; /* jidctred uses islow-style table */ 115 break; 116 #endif 117 case DCTSIZE: 118 switch (cinfo->dct_method) { 119 #ifdef DCT_ISLOW_SUPPORTED 120 case JDCT_ISLOW: 121 method_ptr = jpeg_idct_islow; 122 method = JDCT_ISLOW; 123 break; 124 #endif 125 #ifdef DCT_IFAST_SUPPORTED 126 case JDCT_IFAST: 127 method_ptr = jpeg_idct_ifast; 128 method = JDCT_IFAST; 129 break; 130 #endif 131 #ifdef DCT_FLOAT_SUPPORTED 132 case JDCT_FLOAT: 133 method_ptr = jpeg_idct_float; 134 method = JDCT_FLOAT; 135 break; 136 #endif 137 default: 138 ERREXIT(cinfo, JERR_NOT_COMPILED); 139 break; 140 } 141 break; 142 default: 143 ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size); 144 break; 145 } 146 idct->pub.inverse_DCT[ci] = method_ptr; 147 /* Create multiplier table from quant table. 148 * However, we can skip this if the component is uninteresting 149 * or if we already built the table. Also, if no quant table 150 * has yet been saved for the component, we leave the 151 * multiplier table all-zero; we'll be reading zeroes from the 152 * coefficient controller's buffer anyway. 153 */ 154 if (! compptr->component_needed || idct->cur_method[ci] == method) 155 continue; 156 qtbl = compptr->quant_table; 157 if (qtbl == NULL) /* happens if no data yet for component */ 158 continue; 159 idct->cur_method[ci] = method; 160 switch (method) { 161 #ifdef PROVIDE_ISLOW_TABLES 162 case JDCT_ISLOW: 163 { 164 /* For LL&M IDCT method, multipliers are equal to raw quantization 165 * coefficients, but are stored as ints to ensure access efficiency. 166 */ 167 ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table; 168 for (i = 0; i < DCTSIZE2; i++) { 169 ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i]; 170 } 171 } 172 break; 173 #endif 174 #ifdef DCT_IFAST_SUPPORTED 175 case JDCT_IFAST: 176 { 177 /* For AA&N IDCT method, multipliers are equal to quantization 178 * coefficients scaled by scalefactor[row]*scalefactor[col], where 179 * scalefactor[0] = 1 180 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 181 * For integer operation, the multiplier table is to be scaled by 182 * IFAST_SCALE_BITS. 183 */ 184 IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table; 185 #define CONST_BITS 14 186 static const INT16 aanscales[DCTSIZE2] = { 187 /* precomputed values scaled up by 14 bits */ 188 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, 189 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270, 190 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906, 191 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315, 192 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, 193 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552, 194 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446, 195 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247 196 }; 197 SHIFT_TEMPS 198 199 for (i = 0; i < DCTSIZE2; i++) { 200 ifmtbl[i] = (IFAST_MULT_TYPE) 201 DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], 202 (INT32) aanscales[i]), 203 CONST_BITS-IFAST_SCALE_BITS); 204 } 205 } 206 break; 207 #endif 208 #ifdef DCT_FLOAT_SUPPORTED 209 case JDCT_FLOAT: 210 { 211 /* For float AA&N IDCT method, multipliers are equal to quantization 212 * coefficients scaled by scalefactor[row]*scalefactor[col], where 213 * scalefactor[0] = 1 214 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 215 */ 216 FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table; 217 int row, col; 218 static const double aanscalefactor[DCTSIZE] = { 219 1.0, 1.387039845, 1.306562965, 1.175875602, 220 1.0, 0.785694958, 0.541196100, 0.275899379 221 }; 222 223 i = 0; 224 for (row = 0; row < DCTSIZE; row++) { 225 for (col = 0; col < DCTSIZE; col++) { 226 fmtbl[i] = (FLOAT_MULT_TYPE) 227 ((double) qtbl->quantval[i] * 228 aanscalefactor[row] * aanscalefactor[col]); 229 i++; 230 } 231 } 232 } 233 break; 234 #endif 235 default: 236 ERREXIT(cinfo, JERR_NOT_COMPILED); 237 break; 238 } 239 } 240 } 241 242 243 /* 244 * Initialize IDCT manager. 245 */ 246 247 GLOBAL(void) 248 jinit_inverse_dct (j_decompress_ptr cinfo) 249 { 250 my_idct_ptr idct; 251 int ci; 252 jpeg_component_info *compptr; 253 254 idct = (my_idct_ptr) 255 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 256 SIZEOF(my_idct_controller)); 257 cinfo->idct = (struct jpeg_inverse_dct *) idct; 258 idct->pub.start_pass = start_pass; 259 260 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 261 ci++, compptr++) { 262 /* Allocate and pre-zero a multiplier table for each component */ 263 compptr->dct_table = 264 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 265 SIZEOF(multiplier_table)); 266 MEMZERO(compptr->dct_table, SIZEOF(multiplier_table)); 267 /* Mark multiplier table not yet set up for any method */ 268 idct->cur_method[ci] = -1; 269 } 270 } 271 272 #endif //_FX_JPEG_TURBO_ 273
