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)
start_pass(j_decompress_ptr cinfo)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)
jinit_inverse_dct(j_decompress_ptr cinfo)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