1 : /*
2 : * jddctmgr.c
3 : *
4 : * Copyright (C) 1994-1996, Thomas G. Lane.
5 : * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
6 : * Copyright (C) 2010, D. R. Commander.
7 : * This file is part of the Independent JPEG Group's software.
8 : * For conditions of distribution and use, see the accompanying README file.
9 : *
10 : * This file contains the inverse-DCT management logic.
11 : * This code selects a particular IDCT implementation to be used,
12 : * and it performs related housekeeping chores. No code in this file
13 : * is executed per IDCT step, only during output pass setup.
14 : *
15 : * Note that the IDCT routines are responsible for performing coefficient
16 : * dequantization as well as the IDCT proper. This module sets up the
17 : * dequantization multiplier table needed by the IDCT routine.
18 : */
19 :
20 : #define JPEG_INTERNALS
21 : #include "jinclude.h"
22 : #include "jpeglib.h"
23 : #include "jdct.h" /* Private declarations for DCT subsystem */
24 : #include "jsimddct.h"
25 : #include "jpegcomp.h"
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 :
47 : typedef 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 :
58 : typedef my_idct_controller * my_idct_ptr;
59 :
60 :
61 : /* Allocated multiplier tables: big enough for any supported variant */
62 :
63 : typedef 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 :
92 : METHODDEF(void)
93 5 : start_pass (j_decompress_ptr cinfo)
94 : {
95 5 : my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
96 : int ci, i;
97 : jpeg_component_info *compptr;
98 5 : int method = 0;
99 5 : inverse_DCT_method_ptr method_ptr = NULL;
100 : JQUANT_TBL * qtbl;
101 :
102 25 : for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
103 15 : ci++, compptr++) {
104 : /* Select the proper IDCT routine for this component's scaling */
105 15 : switch (compptr->_DCT_scaled_size) {
106 : #ifdef IDCT_SCALING_SUPPORTED
107 : case 1:
108 0 : method_ptr = jpeg_idct_1x1;
109 0 : method = JDCT_ISLOW; /* jidctred uses islow-style table */
110 0 : break;
111 : case 2:
112 0 : if (jsimd_can_idct_2x2())
113 0 : method_ptr = jsimd_idct_2x2;
114 : else
115 0 : method_ptr = jpeg_idct_2x2;
116 0 : method = JDCT_ISLOW; /* jidctred uses islow-style table */
117 0 : break;
118 : case 4:
119 0 : if (jsimd_can_idct_4x4())
120 0 : method_ptr = jsimd_idct_4x4;
121 : else
122 0 : method_ptr = jpeg_idct_4x4;
123 0 : method = JDCT_ISLOW; /* jidctred uses islow-style table */
124 0 : break;
125 : #endif
126 : case DCTSIZE:
127 15 : switch (cinfo->dct_method) {
128 : #ifdef DCT_ISLOW_SUPPORTED
129 : case JDCT_ISLOW:
130 15 : if (jsimd_can_idct_islow())
131 15 : method_ptr = jsimd_idct_islow;
132 : else
133 0 : method_ptr = jpeg_idct_islow;
134 15 : method = JDCT_ISLOW;
135 15 : break;
136 : #endif
137 : #ifdef DCT_IFAST_SUPPORTED
138 : case JDCT_IFAST:
139 0 : if (jsimd_can_idct_ifast())
140 0 : method_ptr = jsimd_idct_ifast;
141 : else
142 0 : method_ptr = jpeg_idct_ifast;
143 0 : method = JDCT_IFAST;
144 0 : break;
145 : #endif
146 : #ifdef DCT_FLOAT_SUPPORTED
147 : case JDCT_FLOAT:
148 0 : if (jsimd_can_idct_float())
149 0 : method_ptr = jsimd_idct_float;
150 : else
151 0 : method_ptr = jpeg_idct_float;
152 0 : method = JDCT_FLOAT;
153 0 : break;
154 : #endif
155 : default:
156 0 : ERREXIT(cinfo, JERR_NOT_COMPILED);
157 0 : break;
158 : }
159 15 : break;
160 : default:
161 0 : ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->_DCT_scaled_size);
162 0 : break;
163 : }
164 15 : idct->pub.inverse_DCT[ci] = method_ptr;
165 : /* Create multiplier table from quant table.
166 : * However, we can skip this if the component is uninteresting
167 : * or if we already built the table. Also, if no quant table
168 : * has yet been saved for the component, we leave the
169 : * multiplier table all-zero; we'll be reading zeroes from the
170 : * coefficient controller's buffer anyway.
171 : */
172 15 : if (! compptr->component_needed || idct->cur_method[ci] == method)
173 0 : continue;
174 15 : qtbl = compptr->quant_table;
175 15 : if (qtbl == NULL) /* happens if no data yet for component */
176 0 : continue;
177 15 : idct->cur_method[ci] = method;
178 15 : switch (method) {
179 : #ifdef PROVIDE_ISLOW_TABLES
180 : case JDCT_ISLOW:
181 : {
182 : /* For LL&M IDCT method, multipliers are equal to raw quantization
183 : * coefficients, but are stored as ints to ensure access efficiency.
184 : */
185 15 : ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
186 975 : for (i = 0; i < DCTSIZE2; i++) {
187 960 : ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
188 : }
189 : }
190 15 : break;
191 : #endif
192 : #ifdef DCT_IFAST_SUPPORTED
193 : case JDCT_IFAST:
194 : {
195 : /* For AA&N IDCT method, multipliers are equal to quantization
196 : * coefficients scaled by scalefactor[row]*scalefactor[col], where
197 : * scalefactor[0] = 1
198 : * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
199 : * For integer operation, the multiplier table is to be scaled by
200 : * IFAST_SCALE_BITS.
201 : */
202 0 : IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
203 : #define CONST_BITS 14
204 : static const INT16 aanscales[DCTSIZE2] = {
205 : /* precomputed values scaled up by 14 bits */
206 : 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
207 : 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
208 : 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
209 : 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
210 : 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
211 : 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
212 : 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
213 : 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
214 : };
215 : SHIFT_TEMPS
216 :
217 0 : for (i = 0; i < DCTSIZE2; i++) {
218 0 : ifmtbl[i] = (IFAST_MULT_TYPE)
219 0 : DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
220 : (INT32) aanscales[i]),
221 : CONST_BITS-IFAST_SCALE_BITS);
222 : }
223 : }
224 0 : break;
225 : #endif
226 : #ifdef DCT_FLOAT_SUPPORTED
227 : case JDCT_FLOAT:
228 : {
229 : /* For float AA&N IDCT method, multipliers are equal to quantization
230 : * coefficients scaled by scalefactor[row]*scalefactor[col], where
231 : * scalefactor[0] = 1
232 : * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
233 : */
234 0 : FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
235 : int row, col;
236 : static const double aanscalefactor[DCTSIZE] = {
237 : 1.0, 1.387039845, 1.306562965, 1.175875602,
238 : 1.0, 0.785694958, 0.541196100, 0.275899379
239 : };
240 :
241 0 : i = 0;
242 0 : for (row = 0; row < DCTSIZE; row++) {
243 0 : for (col = 0; col < DCTSIZE; col++) {
244 0 : fmtbl[i] = (FLOAT_MULT_TYPE)
245 0 : ((double) qtbl->quantval[i] *
246 0 : aanscalefactor[row] * aanscalefactor[col]);
247 0 : i++;
248 : }
249 : }
250 : }
251 0 : break;
252 : #endif
253 : default:
254 0 : ERREXIT(cinfo, JERR_NOT_COMPILED);
255 0 : break;
256 : }
257 : }
258 5 : }
259 :
260 :
261 : /*
262 : * Initialize IDCT manager.
263 : */
264 :
265 : GLOBAL(void)
266 5 : jinit_inverse_dct (j_decompress_ptr cinfo)
267 : {
268 : my_idct_ptr idct;
269 : int ci;
270 : jpeg_component_info *compptr;
271 :
272 5 : idct = (my_idct_ptr)
273 5 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
274 : SIZEOF(my_idct_controller));
275 5 : cinfo->idct = (struct jpeg_inverse_dct *) idct;
276 5 : idct->pub.start_pass = start_pass;
277 :
278 25 : for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
279 15 : ci++, compptr++) {
280 : /* Allocate and pre-zero a multiplier table for each component */
281 15 : compptr->dct_table =
282 15 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
283 : SIZEOF(multiplier_table));
284 15 : MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
285 : /* Mark multiplier table not yet set up for any method */
286 15 : idct->cur_method[ci] = -1;
287 : }
288 5 : }
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