This is jdsample.c in view mode; [Download] [Up]
/*
* jdsample.c
*
* Copyright (C) 1991, 1992, 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 upsampling routines.
* These routines are invoked via the upsample and
* upsample_init/term methods.
*
* An excellent reference for image resampling is
* Digital Image Warping, George Wolberg, 1990.
* Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
*/
#include "jinclude.h"
/*
* Initialize for upsampling a scan.
*/
METHODDEF void
upsample_init (decompress_info_ptr cinfo)
{
/* no work for now */
}
/*
* Upsample pixel values of a single component.
* This version handles any integral sampling ratios.
*
* This is not used for typical JPEG files, so it need not be fast.
* Nor, for that matter, is it particularly accurate: the algorithm is
* simple replication of the input pixel onto the corresponding output
* pixels. The hi-falutin sampling literature refers to this as a
* "box filter". A box filter tends to introduce visible artifacts,
* so if you are actually going to use 3:1 or 4:1 sampling ratios
* you would be well advised to improve this code.
*/
METHODDEF void
int_upsample (decompress_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];
register JSAMPROW inptr, outptr;
register JSAMPLE invalue;
register short h_expand, h;
short v_expand, v;
int inrow, outrow;
register long incol;
#ifdef DEBUG /* for debugging pipeline controller */
if (input_rows != compptr->v_samp_factor ||
output_rows != cinfo->max_v_samp_factor ||
(input_cols % compptr->h_samp_factor) != 0 ||
(output_cols % cinfo->max_h_samp_factor) != 0 ||
output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
ERREXIT(cinfo->emethods, "Bogus upsample parameters");
#endif
h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
outrow = 0;
for (inrow = 0; inrow < input_rows; inrow++) {
for (v = 0; v < v_expand; v++) {
inptr = input_data[inrow];
outptr = output_data[outrow++];
for (incol = 0; incol < input_cols; incol++) {
invalue = GETJSAMPLE(*inptr++);
for (h = 0; h < h_expand; h++) {
*outptr++ = invalue;
}
}
}
}
}
/*
* Upsample pixel values of a single component.
* This version handles the common case of 2:1 horizontal and 1:1 vertical.
*
* The upsampling algorithm is linear interpolation between pixel centers,
* also known as a "triangle filter". This is a good compromise between
* speed and visual quality. The centers of the output pixels are 1/4 and 3/4
* of the way between input pixel centers.
*/
METHODDEF void
h2v1_upsample (decompress_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)
{
register JSAMPROW inptr, outptr;
register int invalue;
int inrow;
register long colctr;
#ifdef DEBUG /* for debugging pipeline controller */
jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
if (input_rows != compptr->v_samp_factor ||
output_rows != cinfo->max_v_samp_factor ||
(input_cols % compptr->h_samp_factor) != 0 ||
(output_cols % cinfo->max_h_samp_factor) != 0 ||
output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
ERREXIT(cinfo->emethods, "Bogus upsample parameters");
#endif
for (inrow = 0; inrow < input_rows; inrow++) {
inptr = input_data[inrow];
outptr = output_data[inrow];
/* Special case for first column */
invalue = GETJSAMPLE(*inptr++);
*outptr++ = (JSAMPLE) invalue;
*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
for (colctr = input_cols - 2; colctr > 0; colctr--) {
/* General case: 3/4 * nearer pixel + 1/4 * further pixel */
invalue = GETJSAMPLE(*inptr++) * 3;
*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 2) >> 2);
*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
}
/* Special case for last column */
invalue = GETJSAMPLE(*inptr);
*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 2) >> 2);
*outptr++ = (JSAMPLE) invalue;
}
}
/*
* Upsample pixel values of a single component.
* This version handles the common case of 2:1 horizontal and 2:1 vertical.
*
* The upsampling algorithm is linear interpolation between pixel centers,
* also known as a "triangle filter". This is a good compromise between
* speed and visual quality. The centers of the output pixels are 1/4 and 3/4
* of the way between input pixel centers.
*/
METHODDEF void
h2v2_upsample (decompress_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)
{
register JSAMPROW inptr0, inptr1, outptr;
#ifdef EIGHT_BIT_SAMPLES
register int thiscolsum, lastcolsum, nextcolsum;
#else
register INT32 thiscolsum, lastcolsum, nextcolsum;
#endif
int inrow, outrow, v;
register long colctr;
#ifdef DEBUG /* for debugging pipeline controller */
jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
if (input_rows != compptr->v_samp_factor ||
output_rows != cinfo->max_v_samp_factor ||
(input_cols % compptr->h_samp_factor) != 0 ||
(output_cols % cinfo->max_h_samp_factor) != 0 ||
output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
ERREXIT(cinfo->emethods, "Bogus upsample parameters");
#endif
outrow = 0;
for (inrow = 0; inrow < input_rows; inrow++) {
for (v = 0; v < 2; v++) {
/* inptr0 points to nearest input row, inptr1 points to next nearest */
inptr0 = input_data[inrow];
if (v == 0) { /* next nearest is row above */
if (inrow == 0)
inptr1 = above[input_rows-1];
else
inptr1 = input_data[inrow-1];
} else { /* next nearest is row below */
if (inrow == input_rows-1)
inptr1 = below[0];
else
inptr1 = input_data[inrow+1];
}
outptr = output_data[outrow++];
/* Special case for first column */
thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 8) >> 4);
lastcolsum = thiscolsum; thiscolsum = nextcolsum;
for (colctr = input_cols - 2; colctr > 0; colctr--) {
/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 8) >> 4);
lastcolsum = thiscolsum; thiscolsum = nextcolsum;
}
/* Special case for last column */
*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
}
}
}
/*
* Upsample pixel values of a single component.
* This version handles the special case of a full-size component.
*/
METHODDEF void
fullsize_upsample (decompress_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)
{
#ifdef DEBUG /* for debugging pipeline controller */
if (input_cols != output_cols || input_rows != output_rows)
ERREXIT(cinfo->emethods, "Pipeline controller messed up");
#endif
jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
}
/*
* Clean up after a scan.
*/
METHODDEF void
upsample_term (decompress_info_ptr cinfo)
{
/* no work for now */
}
/*
* The method selection routine for upsampling.
* Note that we must select a routine for each component.
*/
GLOBAL void
jselupsample (decompress_info_ptr cinfo)
{
short ci;
jpeg_component_info * compptr;
if (cinfo->CCIR601_sampling)
ERREXIT(cinfo->emethods, "CCIR601 upsampling 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->upsample[ci] = fullsize_upsample;
else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
compptr->v_samp_factor == cinfo->max_v_samp_factor)
cinfo->methods->upsample[ci] = h2v1_upsample;
else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor)
cinfo->methods->upsample[ci] = h2v2_upsample;
else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
(cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
cinfo->methods->upsample[ci] = int_upsample;
else
ERREXIT(cinfo->emethods, "Fractional upsampling not implemented yet");
}
cinfo->methods->upsample_init = upsample_init;
cinfo->methods->upsample_term = upsample_term;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.