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386 lines
15 KiB
C++
386 lines
15 KiB
C++
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/*
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* jcdctmgr.c
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*
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* Copyright (C) 1994-1995, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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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 forward-DCT management logic.
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* This code selects a particular DCT implementation to be used,
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* and it performs related housekeeping chores including coefficient
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* quantization.
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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 "jdct.h" /* Private declarations for DCT subsystem */
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/* Private subobject for this module */
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typedef struct {
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struct jpeg_forward_dct pub;/* public fields */
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/* Pointer to the DCT routine actually in use */
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forward_DCT_method_ptr do_dct;
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/* The actual post-DCT divisors --- not identical to the quant table
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* entries, because of scaling (especially for an unnormalized DCT).
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* Each table is given in normal array order; note that this must
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* be converted from the zigzag order of the quantization tables.
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*/
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DCTELEM * divisors[NUM_QUANT_TBLS];
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#ifdef DCT_FLOAT_SUPPORTED
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/* Same as above for the floating-point case. */
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float_DCT_method_ptr do_float_dct;
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FAST_FLOAT * float_divisors[NUM_QUANT_TBLS];
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#endif
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} my_fdct_controller;
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typedef my_fdct_controller * my_fdct_ptr;
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/*
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* Initialize for a processing pass.
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* Verify that all referenced Q-tables are present, and set up
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* the divisor table for each one.
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* In the current implementation, DCT of all components is done during
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* the first pass, even if only some components will be output in the
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* first scan. Hence all components should be examined here.
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*/
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METHODDEF void
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start_pass_fdctmgr( j_compress_ptr cinfo ) {
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
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int ci, qtblno, i;
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jpeg_component_info * compptr;
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JQUANT_TBL * qtbl;
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//DCTELEM * dtbl;
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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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qtblno = compptr->quant_tbl_no;
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/* Make sure specified quantization table is present */
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if ( ( qtblno < 0 ) || ( qtblno >= NUM_QUANT_TBLS ) ||
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( cinfo->quant_tbl_ptrs[qtblno] == NULL ) ) {
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ERREXIT1( cinfo, JERR_NO_QUANT_TABLE, qtblno );
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}
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qtbl = cinfo->quant_tbl_ptrs[qtblno];
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/* Compute divisors for this quant table */
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/* We may do this more than once for same table, but it's not a big deal */
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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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/* For LL&M IDCT method, divisors are equal to raw quantization
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* coefficients multiplied by 8 (to counteract scaling).
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*/
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if ( fdct->divisors[qtblno] == NULL ) {
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fdct->divisors[qtblno] = (DCTELEM *)
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( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF( DCTELEM ) );
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}
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dtbl = fdct->divisors[qtblno];
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for ( i = 0; i < DCTSIZE2; i++ ) {
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dtbl[i] = ( (DCTELEM) qtbl->quantval[jpeg_zigzag_order[i]] ) << 3;
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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, divisors 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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* We apply a further scale factor of 8.
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*/
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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: in natural order */
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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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if ( fdct->divisors[qtblno] == NULL ) {
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fdct->divisors[qtblno] = (DCTELEM *)
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( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF( DCTELEM ) );
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}
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dtbl = fdct->divisors[qtblno];
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for ( i = 0; i < DCTSIZE2; i++ ) {
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dtbl[i] = (DCTELEM)
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DESCALE( MULTIPLY16V16( (INT32) qtbl->quantval[jpeg_zigzag_order[i]],
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(INT32) aanscales[i] ),
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CONST_BITS - 3 );
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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, divisors 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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* We apply a further scale factor of 8.
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* What's actually stored is 1/divisor so that the inner loop can
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* use a multiplication rather than a division.
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*/
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FAST_FLOAT * fdtbl;
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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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if ( fdct->float_divisors[qtblno] == NULL ) {
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fdct->float_divisors[qtblno] = (FAST_FLOAT *)
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( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF( FAST_FLOAT ) );
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}
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fdtbl = fdct->float_divisors[qtblno];
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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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fdtbl[i] = (FAST_FLOAT)
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( 1.0 / ( ( (double) qtbl->quantval[jpeg_zigzag_order[i]] *
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aanscalefactor[row] * aanscalefactor[col] * 8.0 ) ) );
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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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* Perform forward DCT on one or more blocks of a component.
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*
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* The input samples are taken from the sample_data[] array starting at
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* position start_row/start_col, and moving to the right for any additional
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* blocks. The quantized coefficients are returned in coef_blocks[].
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*/
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METHODDEF void
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forward_DCT( j_compress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
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JDIMENSION start_row, JDIMENSION start_col,
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JDIMENSION num_blocks ) {
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/* This version is used for integer DCT implementations. */
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/* This routine is heavily used, so it's worth coding it tightly. */
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
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forward_DCT_method_ptr do_dct = fdct->do_dct;
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DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
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DCTELEM workspace[DCTSIZE2];/* work area for FDCT subroutine */
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JDIMENSION bi;
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sample_data += start_row;/* fold in the vertical offset once */
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for ( bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE ) {
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/* Load data into workspace, applying unsigned->signed conversion */
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{ register DCTELEM * workspaceptr;
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register JSAMPROW elemptr;
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register int elemr;
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workspaceptr = workspace;
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for ( elemr = 0; elemr < DCTSIZE; elemr++ ) {
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elemptr = sample_data[elemr] + start_col;
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#if DCTSIZE == 8 /* unroll the inner loop */
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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#else
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{ register int elemc;
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for ( elemc = DCTSIZE; elemc > 0; elemc-- ) {
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*workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
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}
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}
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#endif
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}
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}
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/* Perform the DCT */
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( *do_dct )( workspace );
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/* Quantize/descale the coefficients, and store into coef_blocks[] */
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{ register DCTELEM temp, qval;
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register int i;
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register JCOEFPTR output_ptr = coef_blocks[bi];
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for ( i = 0; i < DCTSIZE2; i++ ) {
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qval = divisors[i];
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temp = workspace[i];
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/* Divide the coefficient value by qval, ensuring proper rounding.
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* Since C does not specify the direction of rounding for negative
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* quotients, we have to force the dividend positive for portability.
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*
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* In most files, at least half of the output values will be zero
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* (at default quantization settings, more like three-quarters...)
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* so we should ensure that this case is fast. On many machines,
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* a comparison is enough cheaper than a divide to make a special test
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* a win. Since both inputs will be nonnegative, we need only test
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* for a < b to discover whether a/b is 0.
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* If your machine's division is fast enough, define FAST_DIVIDE.
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*/
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#ifdef FAST_DIVIDE
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#define DIVIDE_BY( a, b ) a /= b
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#else
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#define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0
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#endif
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if ( temp < 0 ) {
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temp = -temp;
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temp += qval >> 1;/* for rounding */
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DIVIDE_BY( temp, qval );
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temp = -temp;
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} else {
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temp += qval >> 1;/* for rounding */
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DIVIDE_BY( temp, qval );
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}
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output_ptr[i] = (JCOEF) temp;
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}
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}
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}
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}
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#ifdef DCT_FLOAT_SUPPORTED
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METHODDEF void
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forward_DCT_float( j_compress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
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JDIMENSION start_row, JDIMENSION start_col,
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JDIMENSION num_blocks ) {
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/* This version is used for floating-point DCT implementations. */
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/* This routine is heavily used, so it's worth coding it tightly. */
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
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float_DCT_method_ptr do_dct = fdct->do_float_dct;
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FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
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FAST_FLOAT workspace[DCTSIZE2];/* work area for FDCT subroutine */
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JDIMENSION bi;
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sample_data += start_row;/* fold in the vertical offset once */
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for ( bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE ) {
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/* Load data into workspace, applying unsigned->signed conversion */
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{ register FAST_FLOAT * workspaceptr;
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register JSAMPROW elemptr;
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register int elemr;
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workspaceptr = workspace;
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for ( elemr = 0; elemr < DCTSIZE; elemr++ ) {
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elemptr = sample_data[elemr] + start_col;
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#if DCTSIZE == 8 /* unroll the inner loop */
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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*workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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#else
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{ register int elemc;
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for ( elemc = DCTSIZE; elemc > 0; elemc-- ) {
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*workspaceptr++ = (FAST_FLOAT)
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( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
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}
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}
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#endif
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}
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}
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/* Perform the DCT */
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( *do_dct )( workspace );
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/* Quantize/descale the coefficients, and store into coef_blocks[] */
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{ register FAST_FLOAT temp;
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register int i;
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register JCOEFPTR output_ptr = coef_blocks[bi];
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for ( i = 0; i < DCTSIZE2; i++ ) {
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/* Apply the quantization and scaling factor */
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temp = workspace[i] * divisors[i];
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/* Round to nearest integer.
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* Since C does not specify the direction of rounding for negative
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* quotients, we have to force the dividend positive for portability.
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* The maximum coefficient size is +-16K (for 12-bit data), so this
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* code should work for either 16-bit or 32-bit ints.
|
||
|
|
*/
|
||
|
|
output_ptr[i] = (JCOEF) ( (int) ( temp + (FAST_FLOAT) 16384.5 ) - 16384 );
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif /* DCT_FLOAT_SUPPORTED */
|
||
|
|
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Initialize FDCT manager.
|
||
|
|
*/
|
||
|
|
|
||
|
|
GLOBAL void
|
||
|
|
jinit_forward_dct( j_compress_ptr cinfo ) {
|
||
|
|
my_fdct_ptr fdct;
|
||
|
|
int i;
|
||
|
|
|
||
|
|
fdct = (my_fdct_ptr)
|
||
|
|
( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
|
||
|
|
SIZEOF( my_fdct_controller ) );
|
||
|
|
cinfo->fdct = (struct jpeg_forward_dct *) fdct;
|
||
|
|
fdct->pub.start_pass = start_pass_fdctmgr;
|
||
|
|
|
||
|
|
switch ( cinfo->dct_method ) {
|
||
|
|
#ifdef DCT_ISLOW_SUPPORTED
|
||
|
|
case JDCT_ISLOW:
|
||
|
|
fdct->pub.forward_DCT = forward_DCT;
|
||
|
|
fdct->do_dct = jpeg_fdct_islow;
|
||
|
|
break;
|
||
|
|
#endif
|
||
|
|
#ifdef DCT_IFAST_SUPPORTED
|
||
|
|
case JDCT_IFAST:
|
||
|
|
fdct->pub.forward_DCT = forward_DCT;
|
||
|
|
fdct->do_dct = jpeg_fdct_ifast;
|
||
|
|
break;
|
||
|
|
#endif
|
||
|
|
#ifdef DCT_FLOAT_SUPPORTED
|
||
|
|
case JDCT_FLOAT:
|
||
|
|
fdct->pub.forward_DCT = forward_DCT_float;
|
||
|
|
fdct->do_float_dct = jpeg_fdct_float;
|
||
|
|
break;
|
||
|
|
#endif
|
||
|
|
default:
|
||
|
|
ERREXIT( cinfo, JERR_NOT_COMPILED );
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Mark divisor tables unallocated */
|
||
|
|
for ( i = 0; i < NUM_QUANT_TBLS; i++ ) {
|
||
|
|
fdct->divisors[i] = NULL;
|
||
|
|
#ifdef DCT_FLOAT_SUPPORTED
|
||
|
|
fdct->float_divisors[i] = NULL;
|
||
|
|
#endif
|
||
|
|
}
|
||
|
|
}
|