The Independent JPEG Group's JPEG software v4
This commit is contained in:
Thomas G. Lane
DRC
230
jdsample.c
230
jdsample.c
@@ -5,37 +5,48 @@
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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 un-subsampling routines.
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* These routines are invoked via the unsubsample and
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* unsubsample_init/term methods.
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* This file contains upsampling routines.
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* These routines are invoked via the upsample and
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* upsample_init/term methods.
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*
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* An excellent reference for image resampling is
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* Digital Image Warping, George Wolberg, 1990.
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* Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
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*/
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#include "jinclude.h"
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/*
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* Initialize for un-subsampling a scan.
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* Initialize for upsampling a scan.
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*/
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METHODDEF void
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unsubsample_init (decompress_info_ptr cinfo)
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upsample_init (decompress_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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* Un-subsample pixel values of a single component.
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* Upsample pixel values of a single component.
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* This version handles any integral sampling ratios.
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*
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* This is not used for typical JPEG files, so it need not be fast.
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* Nor, for that matter, is it particularly accurate: the algorithm is
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* simple replication of the input pixel onto the corresponding output
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* pixels. The hi-falutin sampling literature refers to this as a
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* "box filter". A box filter tends to introduce visible artifacts,
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* so if you are actually going to use 3:1 or 4:1 sampling ratios
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* you would be well advised to improve this code.
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*/
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METHODDEF void
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int_unsubsample (decompress_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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int_upsample (decompress_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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register JSAMPROW inptr, outptr;
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@@ -51,7 +62,7 @@ int_unsubsample (decompress_info_ptr cinfo, int which_component,
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(input_cols % compptr->h_samp_factor) != 0 ||
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(output_cols % cinfo->max_h_samp_factor) != 0 ||
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output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
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ERREXIT(cinfo->emethods, "Bogus unsubsample parameters");
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ERREXIT(cinfo->emethods, "Bogus upsample parameters");
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#endif
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h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
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@@ -74,95 +85,149 @@ int_unsubsample (decompress_info_ptr cinfo, int which_component,
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/*
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* Un-subsample pixel values of a single component.
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* This version handles the extremely common case of
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* horizontal expansion by 2 and any integral vertical expansion.
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* Upsample pixel values of a single component.
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* This version handles the common case of 2:1 horizontal and 1:1 vertical.
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*
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* The upsampling algorithm is linear interpolation between pixel centers,
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* also known as a "triangle filter". This is a good compromise between
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* speed and visual quality. The centers of the output pixels are 1/4 and 3/4
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* of the way between input pixel centers.
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*/
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METHODDEF void
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h2_unsubsample (decompress_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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h2v1_upsample (decompress_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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register JSAMPROW inptr, outptr;
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register JSAMPLE invalue;
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short v_expand, v;
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int inrow, outrow;
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register long incol;
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register int invalue;
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int inrow;
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register long colctr;
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#ifdef DEBUG /* for debugging pipeline controller */
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jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
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if (input_rows != compptr->v_samp_factor ||
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output_rows != cinfo->max_v_samp_factor ||
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(input_cols % compptr->h_samp_factor) != 0 ||
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(output_cols % cinfo->max_h_samp_factor) != 0 ||
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output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
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ERREXIT(cinfo->emethods, "Bogus unsubsample parameters");
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ERREXIT(cinfo->emethods, "Bogus upsample parameters");
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#endif
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v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
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for (inrow = 0; inrow < input_rows; inrow++) {
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inptr = input_data[inrow];
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outptr = output_data[inrow];
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/* Special case for first column */
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = (JSAMPLE) invalue;
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*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
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/* The subsampled image width will always be a multiple of DCTSIZE,
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* so we can unroll the inner loop.
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for (colctr = input_cols - 2; colctr > 0; colctr--) {
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/* General case: 3/4 * nearer pixel + 1/4 * further pixel */
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invalue = GETJSAMPLE(*inptr++) * 3;
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*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 2) >> 2);
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*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
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}
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/* Special case for last column */
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invalue = GETJSAMPLE(*inptr);
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*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 2) >> 2);
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*outptr++ = (JSAMPLE) invalue;
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}
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}
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/*
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* Upsample pixel values of a single component.
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* This version handles the common case of 2:1 horizontal and 2:1 vertical.
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*
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* The upsampling algorithm is linear interpolation between pixel centers,
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* also known as a "triangle filter". This is a good compromise between
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* speed and visual quality. The centers of the output pixels are 1/4 and 3/4
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* of the way between input pixel centers.
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*/
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METHODDEF void
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h2v2_upsample (decompress_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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register JSAMPROW inptr0, inptr1, outptr;
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#ifdef EIGHT_BIT_SAMPLES
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register int thiscolsum, lastcolsum, nextcolsum;
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#else
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register INT32 thiscolsum, lastcolsum, nextcolsum;
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#endif
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int inrow, outrow, v;
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register long colctr;
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#ifdef DEBUG /* for debugging pipeline controller */
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jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
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if (input_rows != compptr->v_samp_factor ||
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output_rows != cinfo->max_v_samp_factor ||
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(input_cols % compptr->h_samp_factor) != 0 ||
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(output_cols % cinfo->max_h_samp_factor) != 0 ||
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output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
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ERREXIT(cinfo->emethods, "Bogus upsample parameters");
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#endif
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outrow = 0;
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for (inrow = 0; inrow < input_rows; inrow++) {
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for (v = 0; v < v_expand; v++) {
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inptr = input_data[inrow];
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for (v = 0; v < 2; v++) {
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/* inptr0 points to nearest input row, inptr1 points to next nearest */
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inptr0 = input_data[inrow];
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if (v == 0) { /* next nearest is row above */
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if (inrow == 0)
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inptr1 = above[input_rows-1];
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else
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inptr1 = input_data[inrow-1];
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} else { /* next nearest is row below */
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if (inrow == input_rows-1)
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inptr1 = below[0];
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else
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inptr1 = input_data[inrow+1];
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}
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outptr = output_data[outrow++];
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#if DCTSIZE == 8
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for (incol = 0; incol < input_cols; incol += DCTSIZE) {
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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/* Special case for first column */
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thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 8) >> 4);
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lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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for (colctr = input_cols - 2; colctr > 0; colctr--) {
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/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
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/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
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nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 8) >> 4);
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lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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}
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#else /* nonstandard DCTSIZE */
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for (incol = 0; incol < input_cols; incol++) {
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = invalue;
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*outptr++ = invalue;
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}
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#endif
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/* Special case for last column */
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
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}
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}
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}
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/*
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* Un-subsample pixel values of a single component.
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* Upsample 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_unsubsample (decompress_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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fullsize_upsample (decompress_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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#ifdef DEBUG /* for debugging pipeline controller */
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if (input_cols != output_cols || input_rows != output_rows)
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@@ -179,7 +244,7 @@ fullsize_unsubsample (decompress_info_ptr cinfo, int which_component,
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*/
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METHODDEF void
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unsubsample_term (decompress_info_ptr cinfo)
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upsample_term (decompress_info_ptr cinfo)
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{
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/* no work for now */
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}
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@@ -187,34 +252,37 @@ unsubsample_term (decompress_info_ptr cinfo)
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/*
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* The method selection routine for unsubsampling.
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* The method selection routine for upsampling.
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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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jselunsubsample (decompress_info_ptr cinfo)
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jselupsample (decompress_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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ERREXIT(cinfo->emethods, "CCIR601 upsampling 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->unsubsample[ci] = fullsize_unsubsample;
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cinfo->methods->upsample[ci] = fullsize_upsample;
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else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
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(cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
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cinfo->methods->unsubsample[ci] = h2_unsubsample;
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compptr->v_samp_factor == cinfo->max_v_samp_factor)
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cinfo->methods->upsample[ci] = h2v1_upsample;
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else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
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compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor)
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cinfo->methods->upsample[ci] = h2v2_upsample;
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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->unsubsample[ci] = int_unsubsample;
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cinfo->methods->upsample[ci] = int_upsample;
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else
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ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
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ERREXIT(cinfo->emethods, "Fractional upsampling not implemented yet");
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}
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cinfo->methods->unsubsample_init = unsubsample_init;
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cinfo->methods->unsubsample_term = unsubsample_term;
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cinfo->methods->upsample_init = upsample_init;
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cinfo->methods->upsample_term = upsample_term;
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}
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