ec6e451d05
Referring to https://github.com/libjpeg-turbo/libjpeg-turbo/issues/402#issuecomment-768348440 and https://github.com/libjpeg-turbo/libjpeg-turbo/issues/402#issuecomment-770221584 Ken Murchison clarified that it was his intent to release the lossless JPEG patch under the IJG License and that adding his name to the copyright headers would be sufficient to acknowledge that any derivatives are based on his work.
273 lines
8.3 KiB
C
273 lines
8.3 KiB
C
/*
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* jddctmgr.c
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*
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* This file was part of the Independent JPEG Group's software:
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* Copyright (C) 1994-1998, Thomas G. Lane.
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* Lossless JPEG Modifications:
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* Copyright (C) 1999, Ken Murchison.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains the inverse-DCT management logic.
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* This code selects a particular IDCT implementation to be used,
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* and it performs related housekeeping chores. No code in this file
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* is executed per IDCT step, only during output pass setup.
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*
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* Note that the IDCT routines are responsible for performing coefficient
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* dequantization as well as the IDCT proper. This module sets up the
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* dequantization multiplier table needed by the IDCT routine.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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#include "jlossy.h" /* Private declarations for lossy subsystem */
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#include "jdct.h" /* Private declarations for DCT subsystem */
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/*
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* The decompressor input side (jdinput.c) saves away the appropriate
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* quantization table for each component at the start of the first scan
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* involving that component. (This is necessary in order to correctly
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* decode files that reuse Q-table slots.)
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* When we are ready to make an output pass, the saved Q-table is converted
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* to a multiplier table that will actually be used by the IDCT routine.
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* The multiplier table contents are IDCT-method-dependent. To support
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* application changes in IDCT method between scans, we can remake the
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* multiplier tables if necessary.
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* In buffered-image mode, the first output pass may occur before any data
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* has been seen for some components, and thus before their Q-tables have
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* been saved away. To handle this case, multiplier tables are preset
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* to zeroes; the result of the IDCT will be a neutral gray level.
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*/
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/* Private subobject for this module */
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typedef struct {
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/* This array contains the IDCT method code that each multiplier table
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* is currently set up for, or -1 if it's not yet set up.
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* The actual multiplier tables are pointed to by dct_table in the
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* per-component comp_info structures.
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*/
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int cur_method[MAX_COMPONENTS];
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} idct_controller;
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typedef idct_controller * idct_ptr;
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/* Allocated multiplier tables: big enough for any supported variant */
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typedef union {
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ISLOW_MULT_TYPE islow_array[DCTSIZE2];
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#ifdef DCT_IFAST_SUPPORTED
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IFAST_MULT_TYPE ifast_array[DCTSIZE2];
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#endif
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#ifdef DCT_FLOAT_SUPPORTED
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FLOAT_MULT_TYPE float_array[DCTSIZE2];
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#endif
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} multiplier_table;
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/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
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* so be sure to compile that code if either ISLOW or SCALING is requested.
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*/
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#ifdef DCT_ISLOW_SUPPORTED
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#define PROVIDE_ISLOW_TABLES
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#else
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#ifdef IDCT_SCALING_SUPPORTED
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#define PROVIDE_ISLOW_TABLES
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#endif
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#endif
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/*
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* Prepare for an output pass.
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* Here we select the proper IDCT routine for each component and build
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* a matching multiplier table.
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*/
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METHODDEF(void)
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start_pass (j_decompress_ptr cinfo)
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{
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j_lossy_d_ptr lossyd = (j_lossy_d_ptr) cinfo->codec;
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idct_ptr idct = (idct_ptr) lossyd->idct_private;
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int ci, i;
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jpeg_component_info *compptr;
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int method = 0;
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inverse_DCT_method_ptr method_ptr = NULL;
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JQUANT_TBL * qtbl;
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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/* Select the proper IDCT routine for this component's scaling */
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switch (compptr->codec_data_unit) {
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#ifdef IDCT_SCALING_SUPPORTED
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case 1:
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method_ptr = jpeg_idct_1x1;
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method = JDCT_ISLOW; /* jidctred uses islow-style table */
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break;
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case 2:
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method_ptr = jpeg_idct_2x2;
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method = JDCT_ISLOW; /* jidctred uses islow-style table */
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break;
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case 4:
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method_ptr = jpeg_idct_4x4;
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method = JDCT_ISLOW; /* jidctred uses islow-style table */
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break;
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#endif
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case DCTSIZE:
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switch (cinfo->dct_method) {
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#ifdef DCT_ISLOW_SUPPORTED
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case JDCT_ISLOW:
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method_ptr = jpeg_idct_islow;
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method = JDCT_ISLOW;
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break;
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#endif
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#ifdef DCT_IFAST_SUPPORTED
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case JDCT_IFAST:
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method_ptr = jpeg_idct_ifast;
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method = JDCT_IFAST;
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break;
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#endif
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#ifdef DCT_FLOAT_SUPPORTED
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case JDCT_FLOAT:
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method_ptr = jpeg_idct_float;
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method = JDCT_FLOAT;
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break;
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#endif
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default:
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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break;
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}
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break;
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default:
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ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->codec_data_unit);
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break;
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}
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lossyd->inverse_DCT[ci] = method_ptr;
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/* Create multiplier table from quant table.
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* However, we can skip this if the component is uninteresting
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* or if we already built the table. Also, if no quant table
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* has yet been saved for the component, we leave the
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* multiplier table all-zero; we'll be reading zeroes from the
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* coefficient controller's buffer anyway.
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*/
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if (! compptr->component_needed || idct->cur_method[ci] == method)
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continue;
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qtbl = compptr->quant_table;
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if (qtbl == NULL) /* happens if no data yet for component */
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continue;
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idct->cur_method[ci] = method;
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switch (method) {
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#ifdef PROVIDE_ISLOW_TABLES
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case JDCT_ISLOW:
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{
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/* For LL&M IDCT method, multipliers are equal to raw quantization
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* coefficients, but are stored as ints to ensure access efficiency.
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*/
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ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
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for (i = 0; i < DCTSIZE2; i++) {
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ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
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}
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}
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break;
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#endif
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#ifdef DCT_IFAST_SUPPORTED
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case JDCT_IFAST:
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{
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/* For AA&N IDCT method, multipliers are equal to quantization
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* coefficients scaled by scalefactor[row]*scalefactor[col], where
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* scalefactor[0] = 1
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* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
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* For integer operation, the multiplier table is to be scaled by
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* IFAST_SCALE_BITS.
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*/
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IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
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#define CONST_BITS 14
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static const INT16 aanscales[DCTSIZE2] = {
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/* precomputed values scaled up by 14 bits */
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
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22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
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21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
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19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
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12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
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8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
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4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
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};
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SHIFT_TEMPS
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for (i = 0; i < DCTSIZE2; i++) {
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ifmtbl[i] = (IFAST_MULT_TYPE)
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DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
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(INT32) aanscales[i]),
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CONST_BITS-IFAST_SCALE_BITS);
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}
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}
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break;
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#endif
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#ifdef DCT_FLOAT_SUPPORTED
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case JDCT_FLOAT:
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{
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/* For float AA&N IDCT method, multipliers are equal to quantization
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* coefficients scaled by scalefactor[row]*scalefactor[col], where
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* scalefactor[0] = 1
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* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
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*/
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FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
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int row, col;
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static const double aanscalefactor[DCTSIZE] = {
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1.0, 1.387039845, 1.306562965, 1.175875602,
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1.0, 0.785694958, 0.541196100, 0.275899379
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};
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i = 0;
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for (row = 0; row < DCTSIZE; row++) {
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for (col = 0; col < DCTSIZE; col++) {
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fmtbl[i] = (FLOAT_MULT_TYPE)
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((double) qtbl->quantval[i] *
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aanscalefactor[row] * aanscalefactor[col]);
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i++;
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}
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}
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}
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break;
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#endif
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default:
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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break;
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}
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}
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}
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/*
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* Initialize IDCT manager.
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*/
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GLOBAL(void)
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jinit_inverse_dct (j_decompress_ptr cinfo)
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{
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j_lossy_d_ptr lossyd = (j_lossy_d_ptr) cinfo->codec;
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idct_ptr idct;
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int ci;
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jpeg_component_info *compptr;
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idct = (idct_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(idct_controller));
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lossyd->idct_private = (void *) idct;
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lossyd->idct_start_pass = start_pass;
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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/* Allocate and pre-zero a multiplier table for each component */
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compptr->dct_table =
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(multiplier_table));
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MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
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/* Mark multiplier table not yet set up for any method */
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idct->cur_method[ci] = -1;
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}
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}
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