The Independent JPEG Group's JPEG software v4
This commit is contained in:
Thomas G. Lane
DRC
401
jcsample.c
401
jcsample.c
@@ -5,50 +5,72 @@
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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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* This file contains downsampling routines.
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* These routines are invoked via the downsample and
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* downsample_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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* The downsampling algorithm used here is a simple average of the source
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* pixels covered by the output pixel. The hi-falutin sampling literature
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* refers to this as a "box filter". In general the characteristics of a box
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* filter are not very good, but for the specific cases we normally use (1:1
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* and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
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* nearly so bad. If you intend to use other sampling ratios, you'd be well
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* advised to improve this code.
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*
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* A simple input-smoothing capability is provided. This is mainly intended
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* for cleaning up color-dithered GIF input files (if you find it inadequate,
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* we suggest using an external filtering program such as pnmconvol). When
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* enabled, each input pixel P is replaced by a weighted sum of itself and its
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* eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF,
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* where SF = (smoothing_factor / 1024).
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* Currently, smoothing is only supported for 2h2v sampling factors.
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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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* Initialize for downsampling 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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downsample_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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* Downsample pixel values of a single component.
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* This version handles arbitrary integral sampling ratios, without smoothing.
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* Note that this version is not actually used for customary 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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int_downsample (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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long outcol, outcol_h; /* outcol_h == outcol*h_expand */
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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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#ifdef DEBUG /* 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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ERREXIT(cinfo->emethods, "Bogus downsample 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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v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
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@@ -58,10 +80,11 @@ subsample (compress_info_ptr cinfo, int which_component,
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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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for (outcol = 0, outcol_h = 0; outcol < output_cols;
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outcol++, outcol_h += h_expand) {
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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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inptr = input_data[inrow+v] + outcol_h;
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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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@@ -74,30 +97,307 @@ subsample (compress_info_ptr cinfo, int which_component,
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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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* Downsample 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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* without smoothing.
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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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h2v1_downsample (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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int outrow;
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long outcol;
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register JSAMPROW inptr, outptr;
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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 (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 downsample parameters");
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#endif
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for (outrow = 0; outrow < output_rows; outrow++) {
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outptr = output_data[outrow];
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inptr = input_data[outrow];
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for (outcol = 0; outcol < output_cols; outcol++) {
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*outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
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+ 1) >> 1);
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inptr += 2;
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}
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}
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}
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/*
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* Downsample pixel values of a single component.
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* This version handles the standard case of 2:1 horizontal and 2:1 vertical,
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* without smoothing.
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*/
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METHODDEF void
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h2v2_downsample (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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int inrow, outrow;
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long outcol;
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register JSAMPROW inptr0, inptr1, outptr;
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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 (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 downsample parameters");
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#endif
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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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inptr0 = input_data[inrow];
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inptr1 = input_data[inrow+1];
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for (outcol = 0; outcol < output_cols; outcol++) {
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*outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
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GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
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+ 2) >> 2);
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inptr0 += 2; inptr1 += 2;
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}
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inrow += 2;
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}
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}
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/*
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* Downsample 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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* without smoothing.
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*/
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METHODDEF void
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fullsize_downsample (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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#ifdef DEBUG /* for debugging pipeline controller */
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if (input_cols != output_cols || input_rows != output_rows)
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ERREXIT(cinfo->emethods, "Pipeline controller messed up");
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#endif
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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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#ifdef INPUT_SMOOTHING_SUPPORTED
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/*
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* Downsample pixel values of a single component.
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* This version handles the standard case of 2:1 horizontal and 2:1 vertical,
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* with smoothing.
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*/
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METHODDEF void
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h2v2_smooth_downsample (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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int inrow, outrow;
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long colctr;
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register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
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INT32 membersum, neighsum, memberscale, neighscale;
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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 (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 downsample parameters");
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#endif
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/* We don't bother to form the individual "smoothed" input pixel values;
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* we can directly compute the output which is the average of the four
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* smoothed values. Each of the four member pixels contributes a fraction
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* (1-8*SF) to its own smoothed image and a fraction SF to each of the three
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* other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
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* output. The four corner-adjacent neighbor pixels contribute a fraction
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* SF to just one smoothed pixel, or SF/4 to the final output; while the
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* eight edge-adjacent neighbors contribute SF to each of two smoothed
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* pixels, or SF/2 overall. In order to use integer arithmetic, these
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* factors are scaled by 2^16 = 65536.
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* Also recall that SF = smoothing_factor / 1024.
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*/
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memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
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neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
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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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inptr0 = input_data[inrow];
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inptr1 = input_data[inrow+1];
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if (inrow == 0)
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above_ptr = above[input_rows-1];
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else
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above_ptr = input_data[inrow-1];
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if (inrow >= input_rows-2)
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below_ptr = below[0];
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else
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below_ptr = input_data[inrow+2];
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/* Special case for first column: pretend column -1 is same as column 0 */
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membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
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GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
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neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
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GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
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GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
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GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
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neighsum += neighsum;
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neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
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GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
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membersum = membersum * memberscale + neighsum * neighscale;
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*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
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inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
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for (colctr = output_cols - 2; colctr > 0; colctr--) {
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/* sum of pixels directly mapped to this output element */
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membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
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GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
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/* sum of edge-neighbor pixels */
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neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
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GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
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GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
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GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
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/* The edge-neighbors count twice as much as corner-neighbors */
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neighsum += neighsum;
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/* Add in the corner-neighbors */
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neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
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GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
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/* form final output scaled up by 2^16 */
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membersum = membersum * memberscale + neighsum * neighscale;
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/* round, descale and output it */
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*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
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inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
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}
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/* Special case for last column */
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membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
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GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
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neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
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GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
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GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
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GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
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neighsum += neighsum;
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neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
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GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
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membersum = membersum * memberscale + neighsum * neighscale;
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*outptr = (JSAMPLE) ((membersum + 32768L) >> 16);
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inrow += 2;
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}
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}
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/*
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* Downsample 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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* with smoothing.
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*/
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METHODDEF void
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fullsize_smooth_downsample (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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int outrow;
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long colctr;
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register JSAMPROW inptr, above_ptr, below_ptr, outptr;
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INT32 membersum, neighsum, memberscale, neighscale;
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int colsum, lastcolsum, nextcolsum;
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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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ERREXIT(cinfo->emethods, "Pipeline controller messed up");
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#endif
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/* Each of the eight neighbor pixels contributes a fraction SF to the
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* smoothed pixel, while the main pixel contributes (1-8*SF). In order
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* to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
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* Also recall that SF = smoothing_factor / 1024.
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*/
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memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
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neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
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for (outrow = 0; outrow < output_rows; outrow++) {
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outptr = output_data[outrow];
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inptr = input_data[outrow];
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if (outrow == 0)
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above_ptr = above[input_rows-1];
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else
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above_ptr = input_data[outrow-1];
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if (outrow >= input_rows-1)
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below_ptr = below[0];
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else
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below_ptr = input_data[outrow+1];
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/* Special case for first column */
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colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
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GETJSAMPLE(*inptr);
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membersum = GETJSAMPLE(*inptr++);
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nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
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GETJSAMPLE(*inptr);
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neighsum = colsum + (colsum - membersum) + nextcolsum;
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membersum = membersum * memberscale + neighsum * neighscale;
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*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
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lastcolsum = colsum; colsum = nextcolsum;
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for (colctr = output_cols - 2; colctr > 0; colctr--) {
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membersum = GETJSAMPLE(*inptr++);
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above_ptr++; below_ptr++;
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nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
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GETJSAMPLE(*inptr);
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neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
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membersum = membersum * memberscale + neighsum * neighscale;
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*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
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lastcolsum = colsum; colsum = nextcolsum;
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}
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/* Special case for last column */
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membersum = GETJSAMPLE(*inptr);
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neighsum = lastcolsum + (colsum - membersum) + colsum;
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membersum = membersum * memberscale + neighsum * neighscale;
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*outptr = (JSAMPLE) ((membersum + 32768L) >> 16);
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}
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}
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#endif /* INPUT_SMOOTHING_SUPPORTED */
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|
||||
/*
|
||||
* Clean up after a scan.
|
||||
*/
|
||||
|
||||
METHODDEF void
|
||||
subsample_term (compress_info_ptr cinfo)
|
||||
downsample_term (compress_info_ptr cinfo)
|
||||
{
|
||||
/* no work for now */
|
||||
}
|
||||
@@ -105,31 +405,56 @@ subsample_term (compress_info_ptr cinfo)
|
||||
|
||||
|
||||
/*
|
||||
* The method selection routine for subsampling.
|
||||
* The method selection routine for downsampling.
|
||||
* Note that we must select a routine for each component.
|
||||
*/
|
||||
|
||||
GLOBAL void
|
||||
jselsubsample (compress_info_ptr cinfo)
|
||||
jseldownsample (compress_info_ptr cinfo)
|
||||
{
|
||||
short ci;
|
||||
jpeg_component_info * compptr;
|
||||
boolean smoothok = TRUE;
|
||||
|
||||
if (cinfo->CCIR601_sampling)
|
||||
ERREXIT(cinfo->emethods, "CCIR601 subsampling not implemented yet");
|
||||
ERREXIT(cinfo->emethods, "CCIR601 downsampling 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");
|
||||
compptr->v_samp_factor == cinfo->max_v_samp_factor) {
|
||||
#ifdef INPUT_SMOOTHING_SUPPORTED
|
||||
if (cinfo->smoothing_factor)
|
||||
cinfo->methods->downsample[ci] = fullsize_smooth_downsample;
|
||||
else
|
||||
#endif
|
||||
cinfo->methods->downsample[ci] = fullsize_downsample;
|
||||
} else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
|
||||
compptr->v_samp_factor == cinfo->max_v_samp_factor) {
|
||||
smoothok = FALSE;
|
||||
cinfo->methods->downsample[ci] = h2v1_downsample;
|
||||
} else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
|
||||
compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
|
||||
#ifdef INPUT_SMOOTHING_SUPPORTED
|
||||
if (cinfo->smoothing_factor)
|
||||
cinfo->methods->downsample[ci] = h2v2_smooth_downsample;
|
||||
else
|
||||
#endif
|
||||
cinfo->methods->downsample[ci] = h2v2_downsample;
|
||||
} else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
|
||||
(cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
|
||||
smoothok = FALSE;
|
||||
cinfo->methods->downsample[ci] = int_downsample;
|
||||
} else
|
||||
ERREXIT(cinfo->emethods, "Fractional downsampling not implemented yet");
|
||||
}
|
||||
|
||||
cinfo->methods->subsample_init = subsample_init;
|
||||
cinfo->methods->subsample_term = subsample_term;
|
||||
#ifdef INPUT_SMOOTHING_SUPPORTED
|
||||
if (cinfo->smoothing_factor && !smoothok)
|
||||
TRACEMS(cinfo->emethods, 0,
|
||||
"Smoothing not supported with nonstandard sampling ratios");
|
||||
#endif
|
||||
|
||||
cinfo->methods->downsample_init = downsample_init;
|
||||
cinfo->methods->downsample_term = downsample_term;
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user