зеркало из https://github.com/mozilla/mozjpeg.git
128 строки
3.9 KiB
C
128 строки
3.9 KiB
C
/*
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* jcmaster.c
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*
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* Copyright (C) 1991, 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 main control for the JPEG compressor.
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* The system-dependent (user interface) code should call jpeg_compress()
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* after doing appropriate setup of the compress_info_struct parameter.
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*/
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#include "jinclude.h"
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METHODDEF void
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c_per_scan_method_selection (compress_info_ptr cinfo)
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/* Central point for per-scan method selection */
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{
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/* Edge expansion */
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jselexpand(cinfo);
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/* Subsampling of pixels */
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jselsubsample(cinfo);
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/* MCU extraction */
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jselcmcu(cinfo);
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}
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LOCAL void
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c_initial_method_selection (compress_info_ptr cinfo)
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/* Central point for initial method selection */
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{
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/* Input image reading method selection is already done. */
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/* So is output file header formatting (both are done by user interface). */
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/* Gamma and color space conversion */
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jselccolor(cinfo);
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/* Entropy encoding: either Huffman or arithmetic coding. */
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#ifdef ARITH_CODING_SUPPORTED
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jselcarithmetic(cinfo);
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#else
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cinfo->arith_code = FALSE; /* force Huffman mode */
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#endif
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jselchuffman(cinfo);
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/* Pipeline control */
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jselcpipeline(cinfo);
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/* Overall control (that's me!) */
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cinfo->methods->c_per_scan_method_selection = c_per_scan_method_selection;
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}
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LOCAL void
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initial_setup (compress_info_ptr cinfo)
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/* Do computations that are needed before initial method selection */
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{
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short 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; ci < cinfo->num_components; ci++) {
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compptr = &cinfo->comp_info[ci];
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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->emethods, "Bogus sampling factors");
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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 logical subsampled dimensions of components */
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for (ci = 0; ci < cinfo->num_components; ci++) {
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compptr = &cinfo->comp_info[ci];
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compptr->true_comp_width = (cinfo->image_width * compptr->h_samp_factor
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+ cinfo->max_h_samp_factor - 1)
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/ cinfo->max_h_samp_factor;
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compptr->true_comp_height = (cinfo->image_height * compptr->v_samp_factor
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+ cinfo->max_v_samp_factor - 1)
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/ cinfo->max_v_samp_factor;
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}
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}
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/*
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* This is the main entry point to the JPEG compressor.
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*/
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GLOBAL void
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jpeg_compress (compress_info_ptr cinfo)
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{
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/* Read the input file header: determine image size & component count.
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* NOTE: the user interface must have initialized the input_init method
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* pointer (eg, by calling jselrppm) before calling me.
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* The other file reading methods (get_input_row etc.) were probably
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* set at the same time, but could be set up by input_init itself,
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* or by c_ui_method_selection.
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*/
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(*cinfo->methods->input_init) (cinfo);
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/* Give UI a chance to adjust compression parameters and select */
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/* output file format based on results of input_init. */
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(*cinfo->methods->c_ui_method_selection) (cinfo);
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/* Now select methods for compression steps. */
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initial_setup(cinfo);
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c_initial_method_selection(cinfo);
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/* Initialize the output file & other modules as needed */
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/* (entropy_encoder is inited by pipeline controller) */
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(*cinfo->methods->colorin_init) (cinfo);
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(*cinfo->methods->write_file_header) (cinfo);
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/* And let the pipeline controller do the rest. */
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(*cinfo->methods->c_pipeline_controller) (cinfo);
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/* Finish output file, release working storage, etc */
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(*cinfo->methods->write_file_trailer) (cinfo);
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(*cinfo->methods->colorin_term) (cinfo);
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(*cinfo->methods->input_term) (cinfo);
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/* My, that was easy, wasn't it? */
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}
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