1 line
17 KiB
C
1 line
17 KiB
C
/*
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* jdmaster.c
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*
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* Copyright (C) 1991-1994, 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 master control logic for the JPEG decompressor.
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* These routines are concerned with selecting the modules to be executed
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* and with determining the number of passes and the work to be done in each
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* pass.
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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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/* Private state */
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typedef struct {
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struct jpeg_decomp_master pub; /* public fields */
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int pass_number; /* probably need more complex state... */
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boolean really_two_pass; /* T if using full two-pass quantization */
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} my_decomp_master;
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typedef my_decomp_master * my_master_ptr;
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/*
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* Support routines that do various essential calculations.
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*
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* jpeg_calc_output_dimensions is exported for possible use by application.
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* Hence it mustn't do anything that can't be done twice.
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*/
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GLOBAL void
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jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
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/* Do computations that are needed before master selection phase */
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{
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int ci;
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jpeg_component_info *compptr;
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/* Compute maximum sampling factors; check factor validity */
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cinfo->max_h_samp_factor = 1;
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cinfo->max_v_samp_factor = 1;
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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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if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
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compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
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ERREXIT(cinfo, JERR_BAD_SAMPLING);
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cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
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compptr->h_samp_factor);
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cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
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compptr->v_samp_factor);
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}
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/* Compute actual output image dimensions and DCT scaling choices. */
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#ifdef IDCT_SCALING_SUPPORTED
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if (cinfo->scale_num * 8 <= cinfo->scale_denom) {
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/* Provide 1/8 scaling */
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cinfo->output_width = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width, 8L);
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cinfo->output_height = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height, 8L);
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cinfo->min_DCT_scaled_size = 1;
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} else if (cinfo->scale_num * 4 <= cinfo->scale_denom) {
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/* Provide 1/4 scaling */
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cinfo->output_width = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width, 4L);
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cinfo->output_height = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height, 4L);
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cinfo->min_DCT_scaled_size = 2;
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} else if (cinfo->scale_num * 2 <= cinfo->scale_denom) {
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/* Provide 1/2 scaling */
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cinfo->output_width = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width, 2L);
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cinfo->output_height = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height, 2L);
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cinfo->min_DCT_scaled_size = 4;
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} else {
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/* Provide 1/1 scaling */
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cinfo->output_width = cinfo->image_width;
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cinfo->output_height = cinfo->image_height;
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cinfo->min_DCT_scaled_size = DCTSIZE;
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}
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/* In selecting the actual DCT scaling for each component, we try to
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* scale up the chroma components via IDCT scaling rather than upsampling.
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* This saves time if the upsampler gets to use 1:1 scaling.
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* Note this code assumes that the supported DCT scalings are powers of 2.
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*/
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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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int ssize = cinfo->min_DCT_scaled_size;
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while (ssize < DCTSIZE &&
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(compptr->h_samp_factor * ssize * 2 <=
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cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) &&
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(compptr->v_samp_factor * ssize * 2 <=
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cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) {
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ssize = ssize * 2;
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}
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compptr->DCT_scaled_size = ssize;
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}
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#else /* !IDCT_SCALING_SUPPORTED */
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/* Hardwire it to "no scaling" */
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cinfo->output_width = cinfo->image_width;
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cinfo->output_height = cinfo->image_height;
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cinfo->min_DCT_scaled_size = DCTSIZE;
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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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compptr->DCT_scaled_size = DCTSIZE;
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}
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#endif /* IDCT_SCALING_SUPPORTED */
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/* Upsample controller really ought to be setting this... */
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cinfo->rec_outbuf_height = 1;
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/* Report number of components in selected colorspace. */
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/* Probably this should be in the color conversion module... */
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switch (cinfo->out_color_space) {
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case JCS_GRAYSCALE:
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cinfo->out_color_components = 1;
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break;
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case JCS_RGB:
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case JCS_YCbCr:
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cinfo->out_color_components = 3;
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break;
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case JCS_CMYK:
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case JCS_YCCK:
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cinfo->out_color_components = 4;
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break;
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default: /* else must be same colorspace as in file */
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cinfo->out_color_components = cinfo->num_components;
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break;
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}
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cinfo->output_components = (cinfo->quantize_colors ? 1 :
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cinfo->out_color_components);
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/* Compute various sampling-related dimensions.
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* Some of these are of interest to the application if it is dealing with
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* "raw" (not upsampled) output, so we do the calculations here.
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*/
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/* Compute dimensions of components */
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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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/* Size in DCT blocks */
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compptr->width_in_blocks = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
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(long) (cinfo->max_h_samp_factor * DCTSIZE));
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compptr->height_in_blocks = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
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(long) (cinfo->max_v_samp_factor * DCTSIZE));
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/* Size in samples, after IDCT scaling */
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compptr->downsampled_width = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width *
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(long) (compptr->h_samp_factor * compptr->DCT_scaled_size),
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(long) (cinfo->max_h_samp_factor * DCTSIZE));
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compptr->downsampled_height = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height *
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(long) (compptr->v_samp_factor * compptr->DCT_scaled_size),
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(long) (cinfo->max_v_samp_factor * DCTSIZE));
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/* Mark component needed, until color conversion says otherwise */
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compptr->component_needed = TRUE;
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}
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/* Compute number of fully interleaved MCU rows (number of times that
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* main controller will call coefficient controller).
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*/
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cinfo->total_iMCU_rows = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height,
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(long) (cinfo->max_v_samp_factor*DCTSIZE));
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}
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LOCAL void
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per_scan_setup (j_decompress_ptr cinfo)
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/* Do computations that are needed before processing a JPEG scan */
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/* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */
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{
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int ci, mcublks;
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JDIMENSION tmp;
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jpeg_component_info *compptr;
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if (cinfo->comps_in_scan == 1) {
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/* Noninterleaved (single-component) scan */
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compptr = cinfo->cur_comp_info[0];
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/* Overall image size in MCUs */
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cinfo->MCUs_per_row = compptr->width_in_blocks;
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cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
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/* For noninterleaved scan, always one block per MCU */
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compptr->MCU_width = 1;
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compptr->MCU_height = 1;
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compptr->MCU_blocks = 1;
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compptr->MCU_sample_width = compptr->DCT_scaled_size;
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compptr->last_col_width = 1;
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compptr->last_row_height = 1;
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/* Prepare array describing MCU composition */
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cinfo->blocks_in_MCU = 1;
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cinfo->MCU_membership[0] = 0;
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} else {
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/* Interleaved (multi-component) scan */
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if (cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
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ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
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MAX_COMPS_IN_SCAN);
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/* Overall image size in MCUs */
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cinfo->MCUs_per_row = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_width,
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(long) (cinfo->max_h_samp_factor*DCTSIZE));
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cinfo->MCU_rows_in_scan = (JDIMENSION)
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jdiv_round_up((long) cinfo->image_height,
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(long) (cinfo->max_v_samp_factor*DCTSIZE));
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cinfo->blocks_in_MCU = 0;
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for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
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compptr = cinfo->cur_comp_info[ci];
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/* Sampling factors give # of blocks of component in each MCU */
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compptr->MCU_width = compptr->h_samp_factor;
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compptr->MCU_height = compptr->v_samp_factor;
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compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
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compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_scaled_size;
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/* Figure number of non-dummy blocks in last MCU column & row */
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tmp = compptr->width_in_blocks % compptr->MCU_width;
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if (tmp == 0) tmp = compptr->MCU_width;
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compptr->last_col_width = (int) tmp;
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tmp = compptr->height_in_blocks % compptr->MCU_height;
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if (tmp == 0) tmp = compptr->MCU_height;
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compptr->last_row_height = (int) tmp;
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/* Prepare array describing MCU composition */
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mcublks = compptr->MCU_blocks;
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if (cinfo->blocks_in_MCU + mcublks > MAX_BLOCKS_IN_MCU)
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ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
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while (mcublks-- > 0) {
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cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
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}
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}
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}
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}
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/*
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* Several decompression processes need to range-limit values to the range
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* 0..MAXJSAMPLE; the input value may fall somewhat outside this range
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* due to noise introduced by quantization, roundoff error, etc. These
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* processes are inner loops and need to be as fast as possible. On most
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* machines, particularly CPUs with pipelines or instruction prefetch,
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* a (subscript-check-less) C table lookup
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* x = sample_range_limit[x];
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* is faster than explicit tests
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* if (x < 0) x = 0;
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* else if (x > MAXJSAMPLE) x = MAXJSAMPLE;
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* These processes all use a common table prepared by the routine below.
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*
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* For most steps we can mathematically guarantee that the initial value
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* of x is within MAXJSAMPLE+1 of the legal range, so a table running from
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* -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial
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* limiting step (just after the IDCT), a wildly out-of-range value is
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* possible if the input data is corrupt. To avoid any chance of indexing
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* off the end of memory and getting a bad-pointer trap, we perform the
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* post-IDCT limiting thus:
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* x = range_limit[x & MASK];
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* where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
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* samples. Under normal circumstances this is more than enough range and
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* a correct output will be generated; with bogus input data the mask will
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* cause wraparound, and we will safely generate a bogus output.
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* For the post-IDCT step, we want to convert the data from signed to unsigned
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* representation by adding CENTERJSAMPLE at the same time that we limit it.
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* So the post-IDCT limiting table ends up looking like this:
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* CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
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* MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
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* 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
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* 0,1,...,CENTERJSAMPLE-1
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* Negative inputs select values from the upper half of the table after
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* masking.
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*
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* We can save some space by overlapping the start of the post-IDCT table
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* with the simpler range limiting table. The post-IDCT table begins at
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* sample_range_limit + CENTERJSAMPLE.
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*
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* Note that the table is allocated in near data space on PCs; it's small
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* enough and used often enough to justify this.
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*/
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LOCAL void
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prepare_range_limit_table (j_decompress_ptr cinfo)
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/* Allocate and fill in the sample_range_limit table */
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{
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JSAMPLE * table;
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int i;
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table = (JSAMPLE *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
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table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */
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cinfo->sample_range_limit = table;
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/* First segment of "simple" table: limit[x] = 0 for x < 0 */
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MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE));
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/* Main part of "simple" table: limit[x] = x */
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for (i = 0; i <= MAXJSAMPLE; i++)
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table[i] = (JSAMPLE) i;
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table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */
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/* End of simple table, rest of first half of post-IDCT table */
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for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++)
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table[i] = MAXJSAMPLE;
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/* Second half of post-IDCT table */
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MEMZERO(table + (2 * (MAXJSAMPLE+1)),
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(2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
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MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE),
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cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
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}
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/*
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* Master selection of decompression modules.
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* This is done once at the start of processing an image. We determine
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* which modules will be used and give them appropriate initialization calls.
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*
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* Note that this is called only after jpeg_read_header has finished.
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* We therefore know what is in the SOF and (first) SOS markers.
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*/
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LOCAL void
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master_selection (j_decompress_ptr cinfo)
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{
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my_master_ptr master = (my_master_ptr) cinfo->master;
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jpeg_calc_output_dimensions(cinfo);
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prepare_range_limit_table(cinfo);
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master->pass_number = 0;
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master->really_two_pass = FALSE;
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master->pub.eoi_processed = FALSE;
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/* There's not a lot of smarts here right now, but it'll get more
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* complicated when we have multiple implementations available...
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*/
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/* Color quantizer selection */
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if (cinfo->quantize_colors) {
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#ifdef QUANT_2PASS_SUPPORTED
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/* 2-pass quantizer only works in 3-component color space.
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* We use the "2-pass" code in a single pass if a colormap is given.
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*/
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if (cinfo->out_color_components != 3)
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cinfo->two_pass_quantize = FALSE;
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else if (cinfo->colormap != NULL)
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cinfo->two_pass_quantize = TRUE;
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#else
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/* Force 1-pass quantize if we don't have 2-pass code compiled. */
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cinfo->two_pass_quantize = FALSE;
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#endif
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if (cinfo->two_pass_quantize) {
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#ifdef QUANT_2PASS_SUPPORTED
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if (cinfo->colormap == NULL)
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master->really_two_pass = TRUE;
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jinit_2pass_quantizer(cinfo);
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#else
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif
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} else {
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#ifdef QUANT_1PASS_SUPPORTED
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jinit_1pass_quantizer(cinfo);
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#else
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif
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}
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}
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/* Post-processing: in particular, color conversion first */
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jinit_color_deconverter(cinfo);
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jinit_upsampler(cinfo);
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jinit_d_post_controller(cinfo, master->really_two_pass);
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/* Inverse DCT */
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jinit_inverse_dct(cinfo);
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/* Entropy decoding: either Huffman or arithmetic coding. */
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if (cinfo->arith_code) {
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#ifdef D_ARITH_CODING_SUPPORTED
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jinit_arith_decoder(cinfo);
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#else
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ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
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#endif
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} else
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jinit_huff_decoder(cinfo);
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jinit_d_coef_controller(cinfo, FALSE /* for now */);
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jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
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/* We can now tell the memory manager to allocate virtual arrays. */
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(*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
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}
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/*
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* Per-pass setup.
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* This is called at the beginning of each pass. We determine which modules
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* will be active during this pass and give them appropriate start_pass calls.
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* We also set is_last_pass to indicate whether any more passes will be
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* required.
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*/
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METHODDEF void
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prepare_for_pass (j_decompress_ptr cinfo)
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{
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my_master_ptr master = (my_master_ptr) cinfo->master;
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/* ???? JUST A QUICK CROCK FOR NOW ??? */
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/* For now, handle only single interleaved input scan; */
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/* we support two passes for color quantization. */
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switch (master->pass_number) {
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case 0:
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/* Set up for data input pass */
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per_scan_setup(cinfo); /* should do this only if an input pass?? */
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master->pub.is_last_pass = ! master->really_two_pass;
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(*cinfo->cconvert->start_pass) (cinfo);
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(*cinfo->upsample->start_pass) (cinfo);
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if (cinfo->quantize_colors)
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(*cinfo->cquantize->start_pass) (cinfo, master->really_two_pass);
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(*cinfo->post->start_pass) (cinfo,
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(master->really_two_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
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(*cinfo->idct->start_pass) (cinfo);
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(*cinfo->entropy->start_pass) (cinfo);
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|
(*cinfo->coef->start_pass) (cinfo, JBUF_PASS_THRU);
|
|
(*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
|
|
break;
|
|
case 1:
|
|
/* Final pass of 2-pass quantization */
|
|
master->pub.is_last_pass = TRUE;
|
|
(*cinfo->cquantize->start_pass) (cinfo, FALSE);
|
|
(*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
|
|
(*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
|
|
break;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Finish up at end of pass.
|
|
*/
|
|
|
|
METHODDEF void
|
|
finish_pass (j_decompress_ptr cinfo)
|
|
{
|
|
my_master_ptr master = (my_master_ptr) cinfo->master;
|
|
|
|
if (cinfo->quantize_colors)
|
|
(*cinfo->cquantize->finish_pass) (cinfo);
|
|
|
|
master->pass_number++;
|
|
}
|
|
|
|
|
|
/*
|
|
* Initialize master decompression control.
|
|
* This creates my own subrecord and also performs the master selection phase,
|
|
* which causes other modules to create their subrecords.
|
|
*/
|
|
|
|
GLOBAL void
|
|
jinit_master_decompress (j_decompress_ptr cinfo)
|
|
{
|
|
my_master_ptr master;
|
|
|
|
master = (my_master_ptr)
|
|
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
|
|
SIZEOF(my_decomp_master));
|
|
cinfo->master = (struct jpeg_decomp_master *) master;
|
|
master->pub.prepare_for_pass = prepare_for_pass;
|
|
master->pub.finish_pass = finish_pass;
|
|
|
|
master_selection(cinfo);
|
|
}
|