4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1994-1996, Thomas G. Lane.
6 * Modified 2002-2010 by Guido Vollbeding.
7 * libjpeg-turbo Modifications:
8 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
9 * Copyright (C) 2010, D. R. Commander.
10 * Copyright (C) 2013, MIPS Technologies, Inc., California
11 * For conditions of distribution and use, see the accompanying README file.
13 * This file contains the inverse-DCT management logic.
14 * This code selects a particular IDCT implementation to be used,
15 * and it performs related housekeeping chores. No code in this file
16 * is executed per IDCT step, only during output pass setup.
18 * Note that the IDCT routines are responsible for performing coefficient
19 * dequantization as well as the IDCT proper. This module sets up the
20 * dequantization multiplier table needed by the IDCT routine.
23 #define JPEG_INTERNALS
26 #include "jdct.h" /* Private declarations for DCT subsystem */
32 * The decompressor input side (jdinput.c) saves away the appropriate
33 * quantization table for each component at the start of the first scan
34 * involving that component. (This is necessary in order to correctly
35 * decode files that reuse Q-table slots.)
36 * When we are ready to make an output pass, the saved Q-table is converted
37 * to a multiplier table that will actually be used by the IDCT routine.
38 * The multiplier table contents are IDCT-method-dependent. To support
39 * application changes in IDCT method between scans, we can remake the
40 * multiplier tables if necessary.
41 * In buffered-image mode, the first output pass may occur before any data
42 * has been seen for some components, and thus before their Q-tables have
43 * been saved away. To handle this case, multiplier tables are preset
44 * to zeroes; the result of the IDCT will be a neutral gray level.
48 /* Private subobject for this module */
51 struct jpeg_inverse_dct pub; /* public fields */
53 /* This array contains the IDCT method code that each multiplier table
54 * is currently set up for, or -1 if it's not yet set up.
55 * The actual multiplier tables are pointed to by dct_table in the
56 * per-component comp_info structures.
58 int cur_method[MAX_COMPONENTS];
61 typedef my_idct_controller * my_idct_ptr;
64 /* Allocated multiplier tables: big enough for any supported variant */
67 ISLOW_MULT_TYPE islow_array[DCTSIZE2];
68 #ifdef DCT_IFAST_SUPPORTED
69 IFAST_MULT_TYPE ifast_array[DCTSIZE2];
71 #ifdef DCT_FLOAT_SUPPORTED
72 FLOAT_MULT_TYPE float_array[DCTSIZE2];
77 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
78 * so be sure to compile that code if either ISLOW or SCALING is requested.
80 #ifdef DCT_ISLOW_SUPPORTED
81 #define PROVIDE_ISLOW_TABLES
83 #ifdef IDCT_SCALING_SUPPORTED
84 #define PROVIDE_ISLOW_TABLES
90 * Prepare for an output pass.
91 * Here we select the proper IDCT routine for each component and build
92 * a matching multiplier table.
96 start_pass (j_decompress_ptr cinfo)
98 my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
100 jpeg_component_info *compptr;
102 inverse_DCT_method_ptr method_ptr = NULL;
105 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
107 /* Select the proper IDCT routine for this component's scaling */
108 switch (compptr->_DCT_scaled_size) {
109 #ifdef IDCT_SCALING_SUPPORTED
111 method_ptr = jpeg_idct_1x1;
112 method = JDCT_ISLOW; /* jidctred uses islow-style table */
115 if (jsimd_can_idct_2x2())
116 method_ptr = jsimd_idct_2x2;
118 method_ptr = jpeg_idct_2x2;
119 method = JDCT_ISLOW; /* jidctred uses islow-style table */
122 method_ptr = jpeg_idct_3x3;
123 method = JDCT_ISLOW; /* jidctint uses islow-style table */
126 if (jsimd_can_idct_4x4())
127 method_ptr = jsimd_idct_4x4;
129 method_ptr = jpeg_idct_4x4;
130 method = JDCT_ISLOW; /* jidctred uses islow-style table */
133 method_ptr = jpeg_idct_5x5;
134 method = JDCT_ISLOW; /* jidctint uses islow-style table */
137 #if defined(__mips__)
138 if (jsimd_can_idct_6x6())
139 method_ptr = jsimd_idct_6x6;
142 method_ptr = jpeg_idct_6x6;
143 method = JDCT_ISLOW; /* jidctint uses islow-style table */
146 method_ptr = jpeg_idct_7x7;
147 method = JDCT_ISLOW; /* jidctint uses islow-style table */
151 switch (cinfo->dct_method) {
152 #ifdef DCT_ISLOW_SUPPORTED
154 if (jsimd_can_idct_islow())
155 method_ptr = jsimd_idct_islow;
157 method_ptr = jpeg_idct_islow;
161 #ifdef DCT_IFAST_SUPPORTED
163 if (jsimd_can_idct_ifast())
164 method_ptr = jsimd_idct_ifast;
166 method_ptr = jpeg_idct_ifast;
170 #ifdef DCT_FLOAT_SUPPORTED
172 if (jsimd_can_idct_float())
173 method_ptr = jsimd_idct_float;
175 method_ptr = jpeg_idct_float;
180 ERREXIT(cinfo, JERR_NOT_COMPILED);
184 #ifdef IDCT_SCALING_SUPPORTED
186 method_ptr = jpeg_idct_9x9;
187 method = JDCT_ISLOW; /* jidctint uses islow-style table */
190 method_ptr = jpeg_idct_10x10;
191 method = JDCT_ISLOW; /* jidctint uses islow-style table */
194 method_ptr = jpeg_idct_11x11;
195 method = JDCT_ISLOW; /* jidctint uses islow-style table */
198 #if defined(__mips__)
199 if (jsimd_can_idct_12x12())
200 method_ptr = jsimd_idct_12x12;
203 method_ptr = jpeg_idct_12x12;
204 method = JDCT_ISLOW; /* jidctint uses islow-style table */
207 method_ptr = jpeg_idct_13x13;
208 method = JDCT_ISLOW; /* jidctint uses islow-style table */
211 method_ptr = jpeg_idct_14x14;
212 method = JDCT_ISLOW; /* jidctint uses islow-style table */
215 method_ptr = jpeg_idct_15x15;
216 method = JDCT_ISLOW; /* jidctint uses islow-style table */
219 method_ptr = jpeg_idct_16x16;
220 method = JDCT_ISLOW; /* jidctint uses islow-style table */
224 ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->_DCT_scaled_size);
227 idct->pub.inverse_DCT[ci] = method_ptr;
228 /* Create multiplier table from quant table.
229 * However, we can skip this if the component is uninteresting
230 * or if we already built the table. Also, if no quant table
231 * has yet been saved for the component, we leave the
232 * multiplier table all-zero; we'll be reading zeroes from the
233 * coefficient controller's buffer anyway.
235 if (! compptr->component_needed || idct->cur_method[ci] == method)
237 qtbl = compptr->quant_table;
238 if (qtbl == NULL) /* happens if no data yet for component */
240 idct->cur_method[ci] = method;
242 #ifdef PROVIDE_ISLOW_TABLES
245 /* For LL&M IDCT method, multipliers are equal to raw quantization
246 * coefficients, but are stored as ints to ensure access efficiency.
248 ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
249 for (i = 0; i < DCTSIZE2; i++) {
250 ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
255 #ifdef DCT_IFAST_SUPPORTED
258 /* For AA&N IDCT method, multipliers are equal to quantization
259 * coefficients scaled by scalefactor[row]*scalefactor[col], where
261 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
262 * For integer operation, the multiplier table is to be scaled by
265 IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
266 #define CONST_BITS 14
267 static const INT16 aanscales[DCTSIZE2] = {
268 /* precomputed values scaled up by 14 bits */
269 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
270 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
271 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
272 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
273 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
274 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
275 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
276 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
280 for (i = 0; i < DCTSIZE2; i++) {
281 ifmtbl[i] = (IFAST_MULT_TYPE)
282 DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
283 (INT32) aanscales[i]),
284 CONST_BITS-IFAST_SCALE_BITS);
289 #ifdef DCT_FLOAT_SUPPORTED
292 /* For float AA&N IDCT method, multipliers are equal to quantization
293 * coefficients scaled by scalefactor[row]*scalefactor[col], where
295 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
297 FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
299 static const double aanscalefactor[DCTSIZE] = {
300 1.0, 1.387039845, 1.306562965, 1.175875602,
301 1.0, 0.785694958, 0.541196100, 0.275899379
305 for (row = 0; row < DCTSIZE; row++) {
306 for (col = 0; col < DCTSIZE; col++) {
307 fmtbl[i] = (FLOAT_MULT_TYPE)
308 ((double) qtbl->quantval[i] *
309 aanscalefactor[row] * aanscalefactor[col]);
317 ERREXIT(cinfo, JERR_NOT_COMPILED);
325 * Initialize IDCT manager.
329 jinit_inverse_dct (j_decompress_ptr cinfo)
333 jpeg_component_info *compptr;
336 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
337 sizeof(my_idct_controller));
338 cinfo->idct = (struct jpeg_inverse_dct *) idct;
339 idct->pub.start_pass = start_pass;
341 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
343 /* Allocate and pre-zero a multiplier table for each component */
345 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
346 sizeof(multiplier_table));
347 MEMZERO(compptr->dct_table, sizeof(multiplier_table));
348 /* Mark multiplier table not yet set up for any method */
349 idct->cur_method[ci] = -1;