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-rw-r--r--jpeg/jcsample.c545
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diff --git a/jpeg/jcsample.c b/jpeg/jcsample.c
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-/*
- * jcsample.c
- *
- * Copyright (C) 1991-1996, 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 downsampling routines.
- *
- * Downsampling input data is counted in "row groups". A row group
- * is defined to be max_v_samp_factor pixel rows of each component,
- * from which the downsampler produces v_samp_factor sample rows.
- * A single row group is processed in each call to the downsampler module.
- *
- * The downsampler is responsible for edge-expansion of its output data
- * to fill an integral number of DCT blocks horizontally. The source buffer
- * may be modified if it is helpful for this purpose (the source buffer is
- * allocated wide enough to correspond to the desired output width).
- * The caller (the prep controller) is responsible for vertical padding.
- *
- * The downsampler may request "context rows" by setting need_context_rows
- * during startup. In this case, the input arrays will contain at least
- * one row group's worth of pixels above and below the passed-in data;
- * the caller will create dummy rows at image top and bottom by replicating
- * the first or last real pixel row.
- *
- * 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.
- *
- * The downsampling algorithm used here is a simple average of the source
- * pixels covered by the output pixel. The hi-falutin sampling literature
- * refers to this as a "box filter". In general the characteristics of a box
- * filter are not very good, but for the specific cases we normally use (1:1
- * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
- * nearly so bad. If you intend to use other sampling ratios, you'd be well
- * advised to improve this code.
- *
- * A simple input-smoothing capability is provided. This is mainly intended
- * for cleaning up color-dithered GIF input files (if you find it inadequate,
- * we suggest using an external filtering program such as pnmconvol). When
- * enabled, each input pixel P is replaced by a weighted sum of itself and its
- * eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF,
- * where SF = (smoothing_factor / 1024).
- * Currently, smoothing is only supported for 2h2v sampling factors.
- */
-
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
-
-
-/* Pointer to routine to downsample a single component */
-typedef JMETHOD(void, downsample1_ptr,
- (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data));
-
-/* Private subobject */
-
-typedef struct {
- struct jpeg_downsampler pub; /* public fields */
-
- /* Downsampling method pointers, one per component */
- downsample1_ptr methods[MAX_COMPONENTS];
-
- /* Height of an output row group for each component. */
- int rowgroup_height[MAX_COMPONENTS];
-
- /* These arrays save pixel expansion factors so that int_downsample need not
- * recompute them each time. They are unused for other downsampling methods.
- */
- UINT8 h_expand[MAX_COMPONENTS];
- UINT8 v_expand[MAX_COMPONENTS];
-} my_downsampler;
-
-typedef my_downsampler * my_downsample_ptr;
-
-
-/*
- * Initialize for a downsampling pass.
- */
-
-METHODDEF(void)
-start_pass_downsample (j_compress_ptr cinfo)
-{
- /* no work for now */
-}
-
-
-/*
- * Expand a component horizontally from width input_cols to width output_cols,
- * by duplicating the rightmost samples.
- */
-
-LOCAL(void)
-expand_right_edge (JSAMPARRAY image_data, int num_rows,
- JDIMENSION input_cols, JDIMENSION output_cols)
-{
- register JSAMPROW ptr;
- register JSAMPLE pixval;
- register int count;
- int row;
- int numcols = (int) (output_cols - input_cols);
-
- if (numcols > 0) {
- for (row = 0; row < num_rows; row++) {
- ptr = image_data[row] + input_cols;
- pixval = ptr[-1]; /* don't need GETJSAMPLE() here */
- for (count = numcols; count > 0; count--)
- *ptr++ = pixval;
- }
- }
-}
-
-
-/*
- * Do downsampling for a whole row group (all components).
- *
- * In this version we simply downsample each component independently.
- */
-
-METHODDEF(void)
-sep_downsample (j_compress_ptr cinfo,
- JSAMPIMAGE input_buf, JDIMENSION in_row_index,
- JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
-{
- my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
- int ci;
- jpeg_component_info * compptr;
- JSAMPARRAY in_ptr, out_ptr;
-
- for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
- ci++, compptr++) {
- in_ptr = input_buf[ci] + in_row_index;
- out_ptr = output_buf[ci] +
- (out_row_group_index * downsample->rowgroup_height[ci]);
- (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
- }
-}
-
-
-/*
- * Downsample pixel values of a single component.
- * One row group is processed per call.
- * This version handles arbitrary integral sampling ratios, without smoothing.
- * Note that this version is not actually used for customary sampling ratios.
- */
-
-METHODDEF(void)
-int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
- int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
- JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */
- JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
- JSAMPROW inptr, outptr;
- INT32 outvalue;
-
- h_expand = downsample->h_expand[compptr->component_index];
- v_expand = downsample->v_expand[compptr->component_index];
- numpix = h_expand * v_expand;
- numpix2 = numpix/2;
-
- /* Expand input data enough to let all the output samples be generated
- * by the standard loop. Special-casing padded output would be more
- * efficient.
- */
- expand_right_edge(input_data, cinfo->max_v_samp_factor,
- cinfo->image_width, output_cols * h_expand);
-
- inrow = outrow = 0;
- while (inrow < cinfo->max_v_samp_factor) {
- outptr = output_data[outrow];
- for (outcol = 0, outcol_h = 0; outcol < output_cols;
- outcol++, outcol_h += h_expand) {
- outvalue = 0;
- for (v = 0; v < v_expand; v++) {
- inptr = input_data[inrow+v] + outcol_h;
- for (h = 0; h < h_expand; h++) {
- outvalue += (INT32) GETJSAMPLE(*inptr++);
- }
- }
- *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
- }
- inrow += v_expand;
- outrow++;
- }
-}
-
-
-/*
- * Downsample pixel values of a single component.
- * This version handles the special case of a full-size component,
- * without smoothing.
- */
-
-METHODDEF(void)
-fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- /* Copy the data */
- jcopy_sample_rows(input_data, 0, output_data, 0,
- cinfo->max_v_samp_factor, cinfo->image_width);
- /* Edge-expand */
- expand_right_edge(output_data, cinfo->max_v_samp_factor, cinfo->image_width,
- compptr->width_in_blocks * compptr->DCT_h_scaled_size);
-}
-
-
-/*
- * Downsample pixel values of a single component.
- * This version handles the common case of 2:1 horizontal and 1:1 vertical,
- * without smoothing.
- *
- * A note about the "bias" calculations: when rounding fractional values to
- * integer, we do not want to always round 0.5 up to the next integer.
- * If we did that, we'd introduce a noticeable bias towards larger values.
- * Instead, this code is arranged so that 0.5 will be rounded up or down at
- * alternate pixel locations (a simple ordered dither pattern).
- */
-
-METHODDEF(void)
-h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- int inrow;
- JDIMENSION outcol;
- JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
- register JSAMPROW inptr, outptr;
- register int bias;
-
- /* Expand input data enough to let all the output samples be generated
- * by the standard loop. Special-casing padded output would be more
- * efficient.
- */
- expand_right_edge(input_data, cinfo->max_v_samp_factor,
- cinfo->image_width, output_cols * 2);
-
- for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
- outptr = output_data[inrow];
- inptr = input_data[inrow];
- bias = 0; /* bias = 0,1,0,1,... for successive samples */
- for (outcol = 0; outcol < output_cols; outcol++) {
- *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
- + bias) >> 1);
- bias ^= 1; /* 0=>1, 1=>0 */
- inptr += 2;
- }
- }
-}
-
-
-/*
- * Downsample pixel values of a single component.
- * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
- * without smoothing.
- */
-
-METHODDEF(void)
-h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- int inrow, outrow;
- JDIMENSION outcol;
- JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
- register JSAMPROW inptr0, inptr1, outptr;
- register int bias;
-
- /* Expand input data enough to let all the output samples be generated
- * by the standard loop. Special-casing padded output would be more
- * efficient.
- */
- expand_right_edge(input_data, cinfo->max_v_samp_factor,
- cinfo->image_width, output_cols * 2);
-
- inrow = outrow = 0;
- while (inrow < cinfo->max_v_samp_factor) {
- outptr = output_data[outrow];
- inptr0 = input_data[inrow];
- inptr1 = input_data[inrow+1];
- bias = 1; /* bias = 1,2,1,2,... for successive samples */
- for (outcol = 0; outcol < output_cols; outcol++) {
- *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
- GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
- + bias) >> 2);
- bias ^= 3; /* 1=>2, 2=>1 */
- inptr0 += 2; inptr1 += 2;
- }
- inrow += 2;
- outrow++;
- }
-}
-
-
-#ifdef INPUT_SMOOTHING_SUPPORTED
-
-/*
- * Downsample pixel values of a single component.
- * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
- * with smoothing. One row of context is required.
- */
-
-METHODDEF(void)
-h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- int inrow, outrow;
- JDIMENSION colctr;
- JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
- register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
- INT32 membersum, neighsum, memberscale, neighscale;
-
- /* Expand input data enough to let all the output samples be generated
- * by the standard loop. Special-casing padded output would be more
- * efficient.
- */
- expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
- cinfo->image_width, output_cols * 2);
-
- /* We don't bother to form the individual "smoothed" input pixel values;
- * we can directly compute the output which is the average of the four
- * smoothed values. Each of the four member pixels contributes a fraction
- * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
- * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
- * output. The four corner-adjacent neighbor pixels contribute a fraction
- * SF to just one smoothed pixel, or SF/4 to the final output; while the
- * eight edge-adjacent neighbors contribute SF to each of two smoothed
- * pixels, or SF/2 overall. In order to use integer arithmetic, these
- * factors are scaled by 2^16 = 65536.
- * Also recall that SF = smoothing_factor / 1024.
- */
-
- memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
- neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
-
- inrow = outrow = 0;
- while (inrow < cinfo->max_v_samp_factor) {
- outptr = output_data[outrow];
- inptr0 = input_data[inrow];
- inptr1 = input_data[inrow+1];
- above_ptr = input_data[inrow-1];
- below_ptr = input_data[inrow+2];
-
- /* Special case for first column: pretend column -1 is same as column 0 */
- membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
- GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
- neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
- GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
- GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
- GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
- neighsum += neighsum;
- neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
- GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
- membersum = membersum * memberscale + neighsum * neighscale;
- *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
- inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
-
- for (colctr = output_cols - 2; colctr > 0; colctr--) {
- /* sum of pixels directly mapped to this output element */
- membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
- GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
- /* sum of edge-neighbor pixels */
- neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
- GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
- GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
- GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
- /* The edge-neighbors count twice as much as corner-neighbors */
- neighsum += neighsum;
- /* Add in the corner-neighbors */
- neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
- GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
- /* form final output scaled up by 2^16 */
- membersum = membersum * memberscale + neighsum * neighscale;
- /* round, descale and output it */
- *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
- inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
- }
-
- /* Special case for last column */
- membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
- GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
- neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
- GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
- GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
- GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
- neighsum += neighsum;
- neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
- GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
- membersum = membersum * memberscale + neighsum * neighscale;
- *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
-
- inrow += 2;
- outrow++;
- }
-}
-
-
-/*
- * Downsample pixel values of a single component.
- * This version handles the special case of a full-size component,
- * with smoothing. One row of context is required.
- */
-
-METHODDEF(void)
-fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
- JSAMPARRAY input_data, JSAMPARRAY output_data)
-{
- int inrow;
- JDIMENSION colctr;
- JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
- register JSAMPROW inptr, above_ptr, below_ptr, outptr;
- INT32 membersum, neighsum, memberscale, neighscale;
- int colsum, lastcolsum, nextcolsum;
-
- /* Expand input data enough to let all the output samples be generated
- * by the standard loop. Special-casing padded output would be more
- * efficient.
- */
- expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
- cinfo->image_width, output_cols);
-
- /* Each of the eight neighbor pixels contributes a fraction SF to the
- * smoothed pixel, while the main pixel contributes (1-8*SF). In order
- * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
- * Also recall that SF = smoothing_factor / 1024.
- */
-
- memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
- neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
-
- for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
- outptr = output_data[inrow];
- inptr = input_data[inrow];
- above_ptr = input_data[inrow-1];
- below_ptr = input_data[inrow+1];
-
- /* Special case for first column */
- colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
- GETJSAMPLE(*inptr);
- membersum = GETJSAMPLE(*inptr++);
- nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
- GETJSAMPLE(*inptr);
- neighsum = colsum + (colsum - membersum) + nextcolsum;
- membersum = membersum * memberscale + neighsum * neighscale;
- *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
- lastcolsum = colsum; colsum = nextcolsum;
-
- for (colctr = output_cols - 2; colctr > 0; colctr--) {
- membersum = GETJSAMPLE(*inptr++);
- above_ptr++; below_ptr++;
- nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
- GETJSAMPLE(*inptr);
- neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
- membersum = membersum * memberscale + neighsum * neighscale;
- *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
- lastcolsum = colsum; colsum = nextcolsum;
- }
-
- /* Special case for last column */
- membersum = GETJSAMPLE(*inptr);
- neighsum = lastcolsum + (colsum - membersum) + colsum;
- membersum = membersum * memberscale + neighsum * neighscale;
- *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
-
- }
-}
-
-#endif /* INPUT_SMOOTHING_SUPPORTED */
-
-
-/*
- * Module initialization routine for downsampling.
- * Note that we must select a routine for each component.
- */
-
-GLOBAL(void)
-jinit_downsampler (j_compress_ptr cinfo)
-{
- my_downsample_ptr downsample;
- int ci;
- jpeg_component_info * compptr;
- boolean smoothok = TRUE;
- int h_in_group, v_in_group, h_out_group, v_out_group;
-
- downsample = (my_downsample_ptr)
- (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
- SIZEOF(my_downsampler));
- cinfo->downsample = (struct jpeg_downsampler *) downsample;
- downsample->pub.start_pass = start_pass_downsample;
- downsample->pub.downsample = sep_downsample;
- downsample->pub.need_context_rows = FALSE;
-
- if (cinfo->CCIR601_sampling)
- ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
-
- /* Verify we can handle the sampling factors, and set up method pointers */
- for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
- ci++, compptr++) {
- /* Compute size of an "output group" for DCT scaling. This many samples
- * are to be converted from max_h_samp_factor * max_v_samp_factor pixels.
- */
- h_out_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
- cinfo->min_DCT_h_scaled_size;
- v_out_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
- cinfo->min_DCT_v_scaled_size;
- h_in_group = cinfo->max_h_samp_factor;
- v_in_group = cinfo->max_v_samp_factor;
- downsample->rowgroup_height[ci] = v_out_group; /* save for use later */
- if (h_in_group == h_out_group && v_in_group == v_out_group) {
-#ifdef INPUT_SMOOTHING_SUPPORTED
- if (cinfo->smoothing_factor) {
- downsample->methods[ci] = fullsize_smooth_downsample;
- downsample->pub.need_context_rows = TRUE;
- } else
-#endif
- downsample->methods[ci] = fullsize_downsample;
- } else if (h_in_group == h_out_group * 2 &&
- v_in_group == v_out_group) {
- smoothok = FALSE;
- downsample->methods[ci] = h2v1_downsample;
- } else if (h_in_group == h_out_group * 2 &&
- v_in_group == v_out_group * 2) {
-#ifdef INPUT_SMOOTHING_SUPPORTED
- if (cinfo->smoothing_factor) {
- downsample->methods[ci] = h2v2_smooth_downsample;
- downsample->pub.need_context_rows = TRUE;
- } else
-#endif
- downsample->methods[ci] = h2v2_downsample;
- } else if ((h_in_group % h_out_group) == 0 &&
- (v_in_group % v_out_group) == 0) {
- smoothok = FALSE;
- downsample->methods[ci] = int_downsample;
- downsample->h_expand[ci] = (UINT8) (h_in_group / h_out_group);
- downsample->v_expand[ci] = (UINT8) (v_in_group / v_out_group);
- } else
- ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
- }
-
-#ifdef INPUT_SMOOTHING_SUPPORTED
- if (cinfo->smoothing_factor && !smoothok)
- TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
-#endif
-}
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