123 lines
3.3 KiB
C
123 lines
3.3 KiB
C
/*
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* jquant2.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 2-pass color quantization (color mapping) routines.
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* These routines are invoked via the methods color_quant_prescan,
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* color_quant_doit, and color_quant_init/term.
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*/
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#include "jinclude.h"
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#ifdef QUANT_2PASS_SUPPORTED
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/*
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* Initialize for two-pass color quantization.
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*/
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METHODDEF void
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color_quant_init (decompress_info_ptr cinfo)
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{
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TRACEMS(cinfo->emethods, 1, "color_quant_init 2 pass");
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}
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/*
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* Prescan some rows of pixels.
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* Note: this could change the data being written into the big image array,
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* if there were any benefit to doing so. The doit routine is not allowed
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* to modify the big image array, because the memory manager is not required
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* to support multiple write passes on a big image.
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*/
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METHODDEF void
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color_quant_prescan (decompress_info_ptr cinfo, int num_rows,
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JSAMPIMAGE image_data)
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{
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TRACEMS1(cinfo->emethods, 2, "color_quant_prescan %d rows", num_rows);
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}
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/*
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* This routine makes the final pass over the image data.
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* output_workspace is a one-component array of pixel dimensions at least
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* as large as the input image strip; it can be used to hold the converted
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* pixels' colormap indexes.
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*/
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METHODDEF void
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final_pass (decompress_info_ptr cinfo, int num_rows,
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JSAMPIMAGE image_data, JSAMPARRAY output_workspace)
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{
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TRACEMS1(cinfo->emethods, 2, "final_pass %d rows", num_rows);
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/* for debug purposes, just emit input data */
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/* NB: this only works for PPM output */
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(*cinfo->methods->put_pixel_rows) (cinfo, num_rows, image_data);
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}
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/*
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* Perform two-pass quantization: rescan the image data and output the
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* converted data via put_color_map and put_pixel_rows.
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* The source_method is a routine that can scan the image data; it can
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* be called as many times as desired. The processing routine called by
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* source_method has the same interface as color_quantize does in the
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* one-pass case, except it must call put_pixel_rows itself. (This allows
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* me to use multiple passes in which earlier passes don't output anything.)
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*/
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METHODDEF void
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color_quant_doit (decompress_info_ptr cinfo, quantize_caller_ptr source_method)
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{
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TRACEMS(cinfo->emethods, 1, "color_quant_doit 2 pass");
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(*source_method) (cinfo, final_pass);
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}
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/*
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* Finish up at the end of the file.
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*/
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METHODDEF void
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color_quant_term (decompress_info_ptr cinfo)
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{
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TRACEMS(cinfo->emethods, 1, "color_quant_term 2 pass");
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}
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/*
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* Map some rows of pixels to the output colormapped representation.
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* Not used in two-pass case.
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*/
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METHODDEF void
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color_quantize (decompress_info_ptr cinfo, int num_rows,
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JSAMPIMAGE input_data, JSAMPARRAY output_data)
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{
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ERREXIT(cinfo->emethods, "Should not get here!");
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}
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/*
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* The method selection routine for 2-pass color quantization.
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*/
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GLOBAL void
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jsel2quantize (decompress_info_ptr cinfo)
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{
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if (cinfo->two_pass_quantize) {
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/* just one alternative for the moment */
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cinfo->methods->color_quant_init = color_quant_init;
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cinfo->methods->color_quant_prescan = color_quant_prescan;
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cinfo->methods->color_quant_doit = color_quant_doit;
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cinfo->methods->color_quant_term = color_quant_term;
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cinfo->methods->color_quantize = color_quantize;
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}
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}
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#endif /* QUANT_2PASS_SUPPORTED */
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