376 lines
12 KiB
C++
376 lines
12 KiB
C++
// * 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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#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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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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// * 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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METHODDEF void
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start_pass_fdctmgr (j_compress_ptr cinfo)
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{
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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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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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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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#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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FAST_FLOAT * fdtbl;
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int row, col;
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static const DOUBLE aanscalefactor[DCTSIZE] = {
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1.0f, 1.387039845f, 1.306562965f, 1.175875602f,
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1.0f, 0.785694958f, 0.541196100f, 0.275899379f
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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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// * 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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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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{
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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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#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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{
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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.
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output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
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}
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}
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}
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}
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#endif // DCT_FLOAT_SUPPORTED
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// * Initialize FDCT manager.
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GLOBAL void
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jinit_forward_dct (j_compress_ptr cinfo)
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{
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my_fdct_ptr fdct;
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int i;
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fdct = (my_fdct_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(my_fdct_controller));
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cinfo->fdct = (struct jpeg_forward_dct *) fdct;
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fdct->pub.start_pass = start_pass_fdctmgr;
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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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fdct->pub.forward_DCT = forward_DCT;
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fdct->do_dct = jpeg_fdct_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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fdct->pub.forward_DCT = forward_DCT;
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fdct->do_dct = jpeg_fdct_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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fdct->pub.forward_DCT = forward_DCT_float;
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fdct->do_float_dct = jpeg_fdct_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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// Mark divisor tables unallocated
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for (i = 0; i < NUM_QUANT_TBLS; i++) {
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fdct->divisors[i] = NULL;
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#ifdef DCT_FLOAT_SUPPORTED
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fdct->float_divisors[i] = NULL;
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#endif
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}
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}
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