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/*
* jcsample.c
*
* Copyright (C) 1991, Thomas G. Lane.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains subsampling routines.
* These routines are invoked via the subsample and
* subsample_init/term methods.
*/
#include "jinclude.h"
/*
* Initialize for subsampling a scan.
*/
METHODDEF void
subsample_init (compress_info_ptr cinfo)
{
/* no work for now */
}
/*
* Subsample pixel values of a single component.
* This version only handles integral sampling ratios.
*/
METHODDEF void
subsample (compress_info_ptr cinfo, int which_component,
long input_cols, int input_rows,
long output_cols, int output_rows,
JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
JSAMPARRAY output_data)
{
jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
long outcol;
JSAMPROW inptr, outptr;
INT32 outvalue;
/* TEMP FOR DEBUGGING PIPELINE CONTROLLER */
if (output_rows != compptr->v_samp_factor ||
input_rows != cinfo->max_v_samp_factor ||
(output_cols % compptr->h_samp_factor) != 0 ||
(input_cols % cinfo->max_h_samp_factor) != 0 ||
input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor)
ERREXIT(cinfo->emethods, "Bogus subsample parameters");
h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
numpix = h_expand * v_expand;
numpix2 = numpix/2;
inrow = 0;
for (outrow = 0; outrow < output_rows; outrow++) {
outptr = output_data[outrow];
for (outcol = 0; outcol < output_cols; outcol++) {
outvalue = 0;
for (v = 0; v < v_expand; v++) {
inptr = input_data[inrow+v] + (outcol*h_expand);
for (h = 0; h < h_expand; h++) {
outvalue += GETJSAMPLE(*inptr++);
}
}
*outptr++ = (outvalue + numpix2) / numpix;
}
inrow += v_expand;
}
}
/*
* Subsample pixel values of a single component.
* This version handles the special case of a full-size component.
*/
METHODDEF void
fullsize_subsample (compress_info_ptr cinfo, int which_component,
long input_cols, int input_rows,
long output_cols, int output_rows,
JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
JSAMPARRAY output_data)
{
if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */
ERREXIT(cinfo->emethods, "Pipeline controller messed up");
jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
}
/*
* Clean up after a scan.
*/
METHODDEF void
subsample_term (compress_info_ptr cinfo)
{
/* no work for now */
}
/*
* The method selection routine for subsampling.
* Note that we must select a routine for each component.
*/
GLOBAL void
jselsubsample (compress_info_ptr cinfo)
{
short ci;
jpeg_component_info * compptr;
if (cinfo->CCIR601_sampling)
ERREXIT(cinfo->emethods, "CCIR601 subsampling not implemented yet");
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
compptr->v_samp_factor == cinfo->max_v_samp_factor)
cinfo->methods->subsample[ci] = fullsize_subsample;
else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
(cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
cinfo->methods->subsample[ci] = subsample;
else
ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
}
cinfo->methods->subsample_init = subsample_init;
cinfo->methods->subsample_term = subsample_term;
}
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