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e1929140 RR |
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 | ||
43 | typedef 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 | ||
54 | typedef my_idct_controller * my_idct_ptr; | |
55 | ||
56 | ||
57 | /* Allocated multiplier tables: big enough for any supported variant */ | |
58 | ||
59 | typedef 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 | ||
88 | METHODDEF(void) | |
89 | start_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 | ||
246 | GLOBAL(void) | |
247 | jinit_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 | } |