1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jddctmgr.c
7 *
8 * Copyright (C) 1994-1996, 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 "jdct.h"               /* Private declarations for DCT subsystem */
26
27
28/*
29 * The decompressor input side (jdinput.c) saves away the appropriate
30 * quantization table for each component at the start of the first scan
31 * involving that component.  (This is necessary in order to correctly
32 * decode files that reuse Q-table slots.)
33 * When we are ready to make an output pass, the saved Q-table is converted
34 * to a multiplier table that will actually be used by the IDCT routine.
35 * The multiplier table contents are IDCT-method-dependent.  To support
36 * application changes in IDCT method between scans, we can remake the
37 * multiplier tables if necessary.
38 * In buffered-image mode, the first output pass may occur before any data
39 * has been seen for some components, and thus before their Q-tables have
40 * been saved away.  To handle this case, multiplier tables are preset
41 * to zeroes; the result of the IDCT will be a neutral gray level.
42 */
43
44
45/* Private subobject for this module */
46
47typedef struct {
48  struct jpeg_inverse_dct pub;  /* public fields */
49
50  /* This array contains the IDCT method code that each multiplier table
51   * is currently set up for, or -1 if it's not yet set up.
52   * The actual multiplier tables are pointed to by dct_table in the
53   * per-component comp_info structures.
54   */
55  int cur_method[MAX_COMPONENTS];
56} my_idct_controller;
57
58typedef my_idct_controller * my_idct_ptr;
59
60
61/* Allocated multiplier tables: big enough for any supported variant */
62
63typedef union {
64  ISLOW_MULT_TYPE islow_array[DCTSIZE2];
65#ifdef DCT_IFAST_SUPPORTED
66  IFAST_MULT_TYPE ifast_array[DCTSIZE2];
67#endif
68#ifdef DCT_FLOAT_SUPPORTED
69  FLOAT_MULT_TYPE float_array[DCTSIZE2];
70#endif
71} multiplier_table;
72
73
74/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
75 * so be sure to compile that code if either ISLOW or SCALING is requested.
76 */
77#ifdef DCT_ISLOW_SUPPORTED
78#define PROVIDE_ISLOW_TABLES
79#else
80#ifdef IDCT_SCALING_SUPPORTED
81#define PROVIDE_ISLOW_TABLES
82#endif
83#endif
84
85
86/*
87 * Prepare for an output pass.
88 * Here we select the proper IDCT routine for each component and build
89 * a matching multiplier table.
90 */
91
92METHODDEF(void)
93start_pass (j_decompress_ptr cinfo)
94{
95  my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
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->DCT_scaled_size) {
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->DCT_scaled_size);
147      break;
148    }
149    idct->pub.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
250GLOBAL(void)
251jinit_inverse_dct (j_decompress_ptr cinfo)
252{
253  my_idct_ptr idct;
254  int ci;
255  jpeg_component_info *compptr;
256
257  idct = (my_idct_ptr)
258    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
259                                SIZEOF(my_idct_controller));
260  cinfo->idct = (struct jpeg_inverse_dct *) idct;
261  idct->pub.start_pass = start_pass;
262
263  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
264       ci++, compptr++) {
265    /* Allocate and pre-zero a multiplier table for each component */
266    compptr->dct_table =
267      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
268                                  SIZEOF(multiplier_table));
269    MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
270    /* Mark multiplier table not yet set up for any method */
271    idct->cur_method[ci] = -1;
272  }
273}
274