compiler/libjpeg/main/jddctmgr.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jddctmgr.c
   7  *
   8  * Copyright (C) 1994-1998, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains the inverse-DCT management logic.
  13  * This code selects a particular IDCT implementation to be used,
  14  * and it performs related housekeeping chores.  No code in this file
  15  * is executed per IDCT step, only during output pass setup.
  16  *
  17  * Note that the IDCT routines are responsible for performing coefficient
  18  * dequantization as well as the IDCT proper.  This module sets up the
  19  * dequantization multiplier table needed by the IDCT routine.
  20  */
  21
  22 #define JPEG_INTERNALS
  23 #include "jinclude.h"
  24 #include "jpeglib.h"
  25 #include "jlossy.h"             /* Private declarations for lossy subsystem */
  26 #include "jdct.h"               /* Private declarations for DCT subsystem */
  27
  28
  29 /*
  30  * The decompressor input side (jdinput.c) saves away the appropriate
  31  * quantization table for each component at the start of the first scan
  32  * involving that component.  (This is necessary in order to correctly
  33  * decode files that reuse Q-table slots.)
  34  * When we are ready to make an output pass, the saved Q-table is converted
  35  * to a multiplier table that will actually be used by the IDCT routine.
  36  * The multiplier table contents are IDCT-method-dependent.  To support
  37  * application changes in IDCT method between scans, we can remake the
  38  * multiplier tables if necessary.
  39  * In buffered-image mode, the first output pass may occur before any data
  40  * has been seen for some components, and thus before their Q-tables have
  41  * been saved away.  To handle this case, multiplier tables are preset
  42  * to zeroes; the result of the IDCT will be a neutral gray level.
  43  */
  44
  45
  46 /* Private subobject for this module */
  47
  48 typedef struct {
  49   /* This array contains the IDCT method code that each multiplier table
  50    * is currently set up for, or -1 if it's not yet set up.
  51    * The actual multiplier tables are pointed to by dct_table in the
  52    * per-component comp_info structures.
  53    */
  54   int cur_method[MAX_COMPONENTS];
  55 } idct_controller;
  56
  57 typedef idct_controller * idct_ptr;
  58
  59
  60 /* Allocated multiplier tables: big enough for any supported variant */
  61
  62 typedef union {
  63   ISLOW_MULT_TYPE islow_array[DCTSIZE2];
  64 #ifdef DCT_IFAST_SUPPORTED
  65   IFAST_MULT_TYPE ifast_array[DCTSIZE2];
  66 #endif
  67 #ifdef DCT_FLOAT_SUPPORTED
  68   FLOAT_MULT_TYPE float_array[DCTSIZE2];
  69 #endif
  70 } multiplier_table;
  71
  72
  73 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
  74  * so be sure to compile that code if either ISLOW or SCALING is requested.
  75  */
  76 #ifdef DCT_ISLOW_SUPPORTED
  77 #define PROVIDE_ISLOW_TABLES
  78 #else
  79 #ifdef IDCT_SCALING_SUPPORTED
  80 #define PROVIDE_ISLOW_TABLES
  81 #endif
  82 #endif
  83
  84
  85 /*
  86  * Prepare for an output pass.
  87  * Here we select the proper IDCT routine for each component and build
  88  * a matching multiplier table.
  89  */
  90
  91 METHODDEF(void)
  92 start_pass (j_decompress_ptr cinfo)
  93 {
  94   j_lossy_d_ptr lossyd = (j_lossy_d_ptr) cinfo->codec;
  95   idct_ptr idct = (idct_ptr) lossyd->idct_private;
  96   int ci, i;
  97   jpeg_component_info *compptr;
  98   int method = 0;
  99   inverse_DCT_method_ptr method_ptr = NULL;
 100   JQUANT_TBL * qtbl;
 101
 102   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 103        ci++, compptr++) {
 104     /* Select the proper IDCT routine for this component's scaling */
 105     switch (compptr->codec_data_unit) {
 106 #ifdef IDCT_SCALING_SUPPORTED
 107     case 1:
 108       method_ptr = jpeg_idct_1x1;
 109       method = JDCT_ISLOW;      /* jidctred uses islow-style table */
 110       break;
 111     case 2:
 112       method_ptr = jpeg_idct_2x2;
 113       method = JDCT_ISLOW;      /* jidctred uses islow-style table */
 114       break;
 115     case 4:
 116       method_ptr = jpeg_idct_4x4;
 117       method = JDCT_ISLOW;      /* jidctred uses islow-style table */
 118       break;
 119 #endif
 120     case DCTSIZE:
 121       switch (cinfo->dct_method) {
 122 #ifdef DCT_ISLOW_SUPPORTED
 123       case JDCT_ISLOW:
 124         method_ptr = jpeg_idct_islow;
 125         method = JDCT_ISLOW;
 126         break;
 127 #endif
 128 #ifdef DCT_IFAST_SUPPORTED
 129       case JDCT_IFAST:
 130         method_ptr = jpeg_idct_ifast;
 131         method = JDCT_IFAST;
 132         break;
 133 #endif
 134 #ifdef DCT_FLOAT_SUPPORTED
 135       case JDCT_FLOAT:
 136         method_ptr = jpeg_idct_float;
 137         method = JDCT_FLOAT;
 138         break;
 139 #endif
 140       default:
 141         ERREXIT(cinfo, JERR_NOT_COMPILED);
 142         break;
 143       }
 144       break;
 145     default:
 146       ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->codec_data_unit);
 147       break;
 148     }
 149     lossyd->inverse_DCT[ci] = method_ptr;
 150     /* Create multiplier table from quant table.
 151      * However, we can skip this if the component is uninteresting
 152      * or if we already built the table.  Also, if no quant table
 153      * has yet been saved for the component, we leave the
 154      * multiplier table all-zero; we'll be reading zeroes from the
 155      * coefficient controller's buffer anyway.
 156      */
 157     if (! compptr->component_needed || idct->cur_method[ci] == method)
 158       continue;
 159     qtbl = compptr->quant_table;
 160     if (qtbl == NULL)           /* happens if no data yet for component */
 161       continue;
 162     idct->cur_method[ci] = method;
 163     switch (method) {
 164 #ifdef PROVIDE_ISLOW_TABLES
 165     case JDCT_ISLOW:
 166       {
 167         /* For LL&M IDCT method, multipliers are equal to raw quantization
 168          * coefficients, but are stored as ints to ensure access efficiency.
 169          */
 170         ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
 171         for (i = 0; i < DCTSIZE2; i++) {
 172           ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
 173         }
 174       }
 175       break;
 176 #endif
 177 #ifdef DCT_IFAST_SUPPORTED
 178     case JDCT_IFAST:
 179       {
 180         /* For AA&N IDCT method, multipliers are equal to quantization
 181          * coefficients scaled by scalefactor[row]*scalefactor[col], where
 182          *   scalefactor[0] = 1
 183          *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
 184          * For integer operation, the multiplier table is to be scaled by
 185          * IFAST_SCALE_BITS.
 186          */
 187         IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
 188 #define CONST_BITS 14
 189         static const INT16 aanscales[DCTSIZE2] = {
 190           /* precomputed values scaled up by 14 bits */
 191           16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 192           22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
 193           21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
 194           19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
 195           16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 196           12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
 197            8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
 198            4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
 199         };
 200         SHIFT_TEMPS
 201
 202         for (i = 0; i < DCTSIZE2; i++) {
 203           ifmtbl[i] = (IFAST_MULT_TYPE)
 204             DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
 205                                   (INT32) aanscales[i]),
 206                     CONST_BITS-IFAST_SCALE_BITS);
 207         }
 208       }
 209       break;
 210 #endif
 211 #ifdef DCT_FLOAT_SUPPORTED
 212     case JDCT_FLOAT:
 213       {
 214         /* For float AA&N IDCT method, multipliers are equal to quantization
 215          * coefficients scaled by scalefactor[row]*scalefactor[col], where
 216          *   scalefactor[0] = 1
 217          *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
 218          */
 219         FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
 220         int row, col;
 221         static const double aanscalefactor[DCTSIZE] = {
 222           1.0, 1.387039845, 1.306562965, 1.175875602,
 223           1.0, 0.785694958, 0.541196100, 0.275899379
 224         };
 225
 226         i = 0;
 227         for (row = 0; row < DCTSIZE; row++) {
 228           for (col = 0; col < DCTSIZE; col++) {
 229             fmtbl[i] = (FLOAT_MULT_TYPE)
 230               ((double) qtbl->quantval[i] *
 231                aanscalefactor[row] * aanscalefactor[col]);
 232             i++;
 233           }
 234         }
 235       }
 236       break;
 237 #endif
 238     default:
 239       ERREXIT(cinfo, JERR_NOT_COMPILED);
 240       break;
 241     }
 242   }
 243 }
 244
 245
 246 /*
 247  * Initialize IDCT manager.
 248  */
 249
 250 JGLOBAL(void)
 251 jinit_inverse_dct (j_decompress_ptr cinfo)
 252 {
 253   j_lossy_d_ptr lossyd = (j_lossy_d_ptr) cinfo->codec;
 254   idct_ptr idct;
 255   int ci;
 256   jpeg_component_info *compptr;
 257
 258   idct = (idct_ptr)
 259     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 260                                 SIZEOF(idct_controller));
 261   lossyd->idct_private = (void *) idct;
 262   lossyd->idct_start_pass = start_pass;
 263
 264   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 265        ci++, compptr++) {
 266     /* Allocate and pre-zero a multiplier table for each component */
 267     compptr->dct_table =
 268       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 269                                   SIZEOF(multiplier_table));
 270     MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
 271     /* Mark multiplier table not yet set up for any method */
 272     idct->cur_method[ci] = -1;
 273   }
 274 }