source: trunk/libjpeg/jddctmgr.c @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 15 years ago

needed libs update

File size: 8.4 KB
Line 
1/*
2 * jddctmgr.c
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains the inverse-DCT management logic.
9 * This code selects a particular IDCT implementation to be used,
10 * and it performs related housekeeping chores.  No code in this file
11 * is executed per IDCT step, only during output pass setup.
12 *
13 * Note that the IDCT routines are responsible for performing coefficient
14 * dequantization as well as the IDCT proper.  This module sets up the
15 * dequantization multiplier table needed by the IDCT routine.
16 */
17
18#define JPEG_INTERNALS
19#include "jinclude.h"
20#include "jpeglib.h"
21#include "jdct.h"               /* Private declarations for DCT subsystem */
22
23
24/*
25 * The decompressor input side (jdinput.c) saves away the appropriate
26 * quantization table for each component at the start of the first scan
27 * involving that component.  (This is necessary in order to correctly
28 * decode files that reuse Q-table slots.)
29 * When we are ready to make an output pass, the saved Q-table is converted
30 * to a multiplier table that will actually be used by the IDCT routine.
31 * The multiplier table contents are IDCT-method-dependent.  To support
32 * application changes in IDCT method between scans, we can remake the
33 * multiplier tables if necessary.
34 * In buffered-image mode, the first output pass may occur before any data
35 * has been seen for some components, and thus before their Q-tables have
36 * been saved away.  To handle this case, multiplier tables are preset
37 * to zeroes; the result of the IDCT will be a neutral gray level.
38 */
39
40
41/* Private subobject for this module */
42
43typedef struct {
44  struct jpeg_inverse_dct pub;  /* public fields */
45
46  /* This array contains the IDCT method code that each multiplier table
47   * is currently set up for, or -1 if it's not yet set up.
48   * The actual multiplier tables are pointed to by dct_table in the
49   * per-component comp_info structures.
50   */
51  int cur_method[MAX_COMPONENTS];
52} my_idct_controller;
53
54typedef my_idct_controller * my_idct_ptr;
55
56
57/* Allocated multiplier tables: big enough for any supported variant */
58
59typedef union {
60  ISLOW_MULT_TYPE islow_array[DCTSIZE2];
61#ifdef DCT_IFAST_SUPPORTED
62  IFAST_MULT_TYPE ifast_array[DCTSIZE2];
63#endif
64#ifdef DCT_FLOAT_SUPPORTED
65  FLOAT_MULT_TYPE float_array[DCTSIZE2];
66#endif
67} multiplier_table;
68
69
70/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
71 * so be sure to compile that code if either ISLOW or SCALING is requested.
72 */
73#ifdef DCT_ISLOW_SUPPORTED
74#define PROVIDE_ISLOW_TABLES
75#else
76#ifdef IDCT_SCALING_SUPPORTED
77#define PROVIDE_ISLOW_TABLES
78#endif
79#endif
80
81
82/*
83 * Prepare for an output pass.
84 * Here we select the proper IDCT routine for each component and build
85 * a matching multiplier table.
86 */
87
88METHODDEF(void)
89start_pass (j_decompress_ptr cinfo)
90{
91  my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
92  int ci, i;
93  jpeg_component_info *compptr;
94  int method = 0;
95  inverse_DCT_method_ptr method_ptr = NULL;
96  JQUANT_TBL * qtbl;
97
98  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
99       ci++, compptr++) {
100    /* Select the proper IDCT routine for this component's scaling */
101    switch (compptr->DCT_scaled_size) {
102#ifdef IDCT_SCALING_SUPPORTED
103    case 1:
104      method_ptr = jpeg_idct_1x1;
105      method = JDCT_ISLOW;      /* jidctred uses islow-style table */
106      break;
107    case 2:
108      method_ptr = jpeg_idct_2x2;
109      method = JDCT_ISLOW;      /* jidctred uses islow-style table */
110      break;
111    case 4:
112      method_ptr = jpeg_idct_4x4;
113      method = JDCT_ISLOW;      /* jidctred uses islow-style table */
114      break;
115#endif
116    case DCTSIZE:
117      switch (cinfo->dct_method) {
118#ifdef DCT_ISLOW_SUPPORTED
119      case JDCT_ISLOW:
120        method_ptr = jpeg_idct_islow;
121        method = JDCT_ISLOW;
122        break;
123#endif
124#ifdef DCT_IFAST_SUPPORTED
125      case JDCT_IFAST:
126        method_ptr = jpeg_idct_ifast;
127        method = JDCT_IFAST;
128        break;
129#endif
130#ifdef DCT_FLOAT_SUPPORTED
131      case JDCT_FLOAT:
132        method_ptr = jpeg_idct_float;
133        method = JDCT_FLOAT;
134        break;
135#endif
136      default:
137        ERREXIT(cinfo, JERR_NOT_COMPILED);
138        break;
139      }
140      break;
141    default:
142      ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
143      break;
144    }
145    idct->pub.inverse_DCT[ci] = method_ptr;
146    /* Create multiplier table from quant table.
147     * However, we can skip this if the component is uninteresting
148     * or if we already built the table.  Also, if no quant table
149     * has yet been saved for the component, we leave the
150     * multiplier table all-zero; we'll be reading zeroes from the
151     * coefficient controller's buffer anyway.
152     */
153    if (! compptr->component_needed || idct->cur_method[ci] == method)
154      continue;
155    qtbl = compptr->quant_table;
156    if (qtbl == NULL)           /* happens if no data yet for component */
157      continue;
158    idct->cur_method[ci] = method;
159    switch (method) {
160#ifdef PROVIDE_ISLOW_TABLES
161    case JDCT_ISLOW:
162      {
163        /* For LL&M IDCT method, multipliers are equal to raw quantization
164         * coefficients, but are stored as ints to ensure access efficiency.
165         */
166        ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
167        for (i = 0; i < DCTSIZE2; i++) {
168          ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
169        }
170      }
171      break;
172#endif
173#ifdef DCT_IFAST_SUPPORTED
174    case JDCT_IFAST:
175      {
176        /* For AA&N IDCT method, multipliers are equal to quantization
177         * coefficients scaled by scalefactor[row]*scalefactor[col], where
178         *   scalefactor[0] = 1
179         *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
180         * For integer operation, the multiplier table is to be scaled by
181         * IFAST_SCALE_BITS.
182         */
183        IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
184#define CONST_BITS 14
185        static const INT16 aanscales[DCTSIZE2] = {
186          /* precomputed values scaled up by 14 bits */
187          16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
188          22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
189          21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
190          19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
191          16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
192          12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
193           8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
194           4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
195        };
196        SHIFT_TEMPS
197
198        for (i = 0; i < DCTSIZE2; i++) {
199          ifmtbl[i] = (IFAST_MULT_TYPE)
200            DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
201                                  (INT32) aanscales[i]),
202                    CONST_BITS-IFAST_SCALE_BITS);
203        }
204      }
205      break;
206#endif
207#ifdef DCT_FLOAT_SUPPORTED
208    case JDCT_FLOAT:
209      {
210        /* For float AA&N IDCT method, multipliers are equal to quantization
211         * coefficients scaled by scalefactor[row]*scalefactor[col], where
212         *   scalefactor[0] = 1
213         *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
214         */
215        FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
216        int row, col;
217        static const double aanscalefactor[DCTSIZE] = {
218          1.0, 1.387039845, 1.306562965, 1.175875602,
219          1.0, 0.785694958, 0.541196100, 0.275899379
220        };
221
222        i = 0;
223        for (row = 0; row < DCTSIZE; row++) {
224          for (col = 0; col < DCTSIZE; col++) {
225            fmtbl[i] = (FLOAT_MULT_TYPE)
226              ((double) qtbl->quantval[i] *
227               aanscalefactor[row] * aanscalefactor[col]);
228            i++;
229          }
230        }
231      }
232      break;
233#endif
234    default:
235      ERREXIT(cinfo, JERR_NOT_COMPILED);
236      break;
237    }
238  }
239}
240
241
242/*
243 * Initialize IDCT manager.
244 */
245
246GLOBAL(void)
247jinit_inverse_dct (j_decompress_ptr cinfo)
248{
249  my_idct_ptr idct;
250  int ci;
251  jpeg_component_info *compptr;
252
253  idct = (my_idct_ptr)
254    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
255                                SIZEOF(my_idct_controller));
256  cinfo->idct = (struct jpeg_inverse_dct *) idct;
257  idct->pub.start_pass = start_pass;
258
259  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
260       ci++, compptr++) {
261    /* Allocate and pre-zero a multiplier table for each component */
262    compptr->dct_table =
263      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
264                                  SIZEOF(multiplier_table));
265    MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
266    /* Mark multiplier table not yet set up for any method */
267    idct->cur_method[ci] = -1;
268  }
269}
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