133 lines
4.1 KiB
C
133 lines
4.1 KiB
C
/*
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© 2011-2015 by Kornel Lesiński.
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This file is part of libimagequant.
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libimagequant is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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libimagequant is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "libimagequant.h"
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#include "pam.h"
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#include "blur.h"
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/*
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Blurs image horizontally (width 2*size+1) and writes it transposed to dst (called twice gives 2d blur)
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*/
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static void transposing_1d_blur(unsigned char *restrict src, unsigned char *restrict dst, unsigned int width, unsigned int height, const unsigned int size)
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{
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assert(size > 0);
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for(unsigned int j=0; j < height; j++) {
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unsigned char *restrict row = src + j*width;
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// accumulate sum for pixels outside line
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unsigned int sum;
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sum = row[0]*size;
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for(unsigned int i=0; i < size; i++) {
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sum += row[i];
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}
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// blur with left side outside line
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for(unsigned int i=0; i < size; i++) {
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sum -= row[0];
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sum += row[i+size];
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dst[i*height + j] = sum / (size*2);
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}
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for(unsigned int i=size; i < width-size; i++) {
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sum -= row[i-size];
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sum += row[i+size];
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dst[i*height + j] = sum / (size*2);
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}
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// blur with right side outside line
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for(unsigned int i=width-size; i < width; i++) {
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sum -= row[i-size];
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sum += row[width-1];
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dst[i*height + j] = sum / (size*2);
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}
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}
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}
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/**
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* Picks maximum of neighboring pixels (blur + lighten)
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*/
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LIQ_PRIVATE void liq_max3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height)
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{
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for(unsigned int j=0; j < height; j++) {
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const unsigned char *row = src + j*width,
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*prevrow = src + (j > 1 ? j-1 : 0)*width,
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*nextrow = src + MIN(height-1,j+1)*width;
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unsigned char prev,curr=row[0],next=row[0];
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for(unsigned int i=0; i < width-1; i++) {
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prev=curr;
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curr=next;
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next=row[i+1];
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unsigned char t1 = MAX(prev,next);
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unsigned char t2 = MAX(nextrow[i],prevrow[i]);
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*dst++ = MAX(curr,MAX(t1,t2));
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}
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unsigned char t1 = MAX(curr,next);
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unsigned char t2 = MAX(nextrow[width-1],prevrow[width-1]);
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*dst++ = MAX(t1,t2);
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}
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}
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/**
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* Picks minimum of neighboring pixels (blur + darken)
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*/
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LIQ_PRIVATE void liq_min3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height)
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{
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for(unsigned int j=0; j < height; j++) {
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const unsigned char *row = src + j*width,
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*prevrow = src + (j > 1 ? j-1 : 0)*width,
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*nextrow = src + MIN(height-1,j+1)*width;
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unsigned char prev,curr=row[0],next=row[0];
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for(unsigned int i=0; i < width-1; i++) {
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prev=curr;
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curr=next;
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next=row[i+1];
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unsigned char t1 = MIN(prev,next);
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unsigned char t2 = MIN(nextrow[i],prevrow[i]);
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*dst++ = MIN(curr,MIN(t1,t2));
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}
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unsigned char t1 = MIN(curr,next);
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unsigned char t2 = MIN(nextrow[width-1],prevrow[width-1]);
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*dst++ = MIN(t1,t2);
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}
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}
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/*
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Filters src image and saves it to dst, overwriting tmp in the process.
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Image must be width*height pixels high. Size controls radius of box blur.
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*/
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LIQ_PRIVATE void liq_blur(unsigned char *src, unsigned char *tmp, unsigned char *dst, unsigned int width, unsigned int height, unsigned int size)
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{
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assert(size > 0);
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if (width < 2*size+1 || height < 2*size+1) {
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return;
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}
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transposing_1d_blur(src, tmp, width, height, size);
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transposing_1d_blur(tmp, dst, height, width, size);
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}
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