136 lines
3.7 KiB
C
136 lines
3.7 KiB
C
/*
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* jcsample.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 subsampling routines.
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* These routines are invoked via the subsample and
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* subsample_init/term methods.
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*/
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#include "jinclude.h"
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/*
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* Initialize for subsampling a scan.
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*/
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METHODDEF void
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subsample_init (compress_info_ptr cinfo)
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{
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/* no work for now */
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}
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/*
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* Subsample pixel values of a single component.
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* This version only handles integral sampling ratios.
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*/
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METHODDEF void
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subsample (compress_info_ptr cinfo, int which_component,
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long input_cols, int input_rows,
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long output_cols, int output_rows,
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JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
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JSAMPARRAY output_data)
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{
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jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
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int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
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long outcol;
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JSAMPROW inptr, outptr;
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INT32 outvalue;
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/* TEMP FOR DEBUGGING PIPELINE CONTROLLER */
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if (output_rows != compptr->v_samp_factor ||
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input_rows != cinfo->max_v_samp_factor ||
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(output_cols % compptr->h_samp_factor) != 0 ||
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(input_cols % cinfo->max_h_samp_factor) != 0 ||
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input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor)
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ERREXIT(cinfo->emethods, "Bogus subsample parameters");
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h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
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v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
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numpix = h_expand * v_expand;
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numpix2 = numpix/2;
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inrow = 0;
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for (outrow = 0; outrow < output_rows; outrow++) {
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outptr = output_data[outrow];
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for (outcol = 0; outcol < output_cols; outcol++) {
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outvalue = 0;
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for (v = 0; v < v_expand; v++) {
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inptr = input_data[inrow+v] + (outcol*h_expand);
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for (h = 0; h < h_expand; h++) {
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outvalue += (INT32) GETJSAMPLE(*inptr++);
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}
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}
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*outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
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}
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inrow += v_expand;
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}
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}
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/*
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* Subsample pixel values of a single component.
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* This version handles the special case of a full-size component.
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*/
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METHODDEF void
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fullsize_subsample (compress_info_ptr cinfo, int which_component,
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long input_cols, int input_rows,
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long output_cols, int output_rows,
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JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
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JSAMPARRAY output_data)
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{
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if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */
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ERREXIT(cinfo->emethods, "Pipeline controller messed up");
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jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
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}
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/*
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* Clean up after a scan.
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*/
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METHODDEF void
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subsample_term (compress_info_ptr cinfo)
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{
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/* no work for now */
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}
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/*
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* The method selection routine for subsampling.
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* Note that we must select a routine for each component.
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*/
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GLOBAL void
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jselsubsample (compress_info_ptr cinfo)
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{
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short ci;
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jpeg_component_info * compptr;
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if (cinfo->CCIR601_sampling)
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ERREXIT(cinfo->emethods, "CCIR601 subsampling not implemented yet");
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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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if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
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compptr->v_samp_factor == cinfo->max_v_samp_factor)
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cinfo->methods->subsample[ci] = fullsize_subsample;
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else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
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(cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
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cinfo->methods->subsample[ci] = subsample;
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else
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ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
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}
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cinfo->methods->subsample_init = subsample_init;
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cinfo->methods->subsample_term = subsample_term;
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}
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