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greg |
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/*
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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CIQ - main program for color image quantization
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options for Floyd-Steinberg dithering by minimization of accumulated error
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or undithered quantization
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Paul Heckbert 16 April 82, cleaned up 8 June 86
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Greg Ward 1 March 88, modified for arbitrary picture sizes
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*/
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#include "ciq.h"
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#define table(m,r,g,b) hist[m[0][r]|m[1][g]|m[2][b]] /* histogram/pvtable */
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int hist[len]; /* list of frequencies or pixelvalues for coded color */
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colormap color; /* quantization colormap */
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int n; /* number of colors in it */
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/*----------------------------------------------------------------------*/
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ciq(dith,nw,synth,cm)
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int dith; /* is dithering desired? 0=no, 1=yes */
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int nw; /* number of colors wanted in output image */
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int synth; /* synthesize colormap? 0=no, 1=yes */
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colormap cm; /* quantization colormap */
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/* read if synth=0; always written */
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{
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int na,i;
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colormap ocm;
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picreadcm(ocm); /* read original picture's colormap (usually identity)*/
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sample(ocm); /* find histogram */
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if (synth)
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n = makecm(nw,&na); /* analyze histogram and synthesize colormap */
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else {
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bcopy(cm,color,sizeof color);
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n = nw;
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na = 0;
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for (i=0; i<len; i++) if (hist[i]) na++;
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/*printf("from %d to %d colors\n",na,n);*/
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}
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picwritecm(color);
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if (dith)
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draw_dith(ocm);
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else {
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for (i=0; i<len; i++)
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if (hist[i]) hist[i] = closest(red(i),gre(i),blu(i));
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draw_nodith(ocm);
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}
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bcopy(color,cm,sizeof color);
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/*endclosest();*/
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}
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/*----------------------------------------------------------------------*/
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sample(ocm) /* make color frequency table (histogram) */
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colormap ocm;
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{
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register int x,y;
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register rgbpixel *lp;
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rgbpixel *line;
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colormap map;
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line = line3alloc(xmax);
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convertmap(ocm,map);
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for (y=0; y<ymax; y++) {
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picreadline3(y,line);
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for (lp=line, x=0; x<xmax; x++, lp++)
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table(map,lp->r,lp->g,lp->b)++;
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}
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free((char *)line);
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}
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convertmap(in,out) /* convert to shifted color map */
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register colormap in,out;
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{
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register int j;
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for (j=0; j<256; j++) {
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out[0][j] = (in[0][j]&0xf8)<<7;
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out[1][j] = (in[1][j]&0xf8)<<2;
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out[2][j] = (in[2][j]&0xf8)>>3;
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}
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}
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draw_nodith(ocm) /* quantize without dithering */
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colormap ocm; /* colormap for orig */
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{
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register int x,y;
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register rgbpixel *lp;
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rgbpixel *iline;
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pixel *oline;
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colormap map;
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iline = line3alloc(xmax);
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oline = linealloc(xmax);
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convertmap(ocm,map);
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for (y=0; y<ymax; y++) {
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picreadline3(y,iline);
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for (lp=iline, x=0; x<xmax; x++, lp++)
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oline[x] = table(map,lp->r,lp->g,lp->b);
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picwriteline(y,oline);
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}
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free((char *)iline);
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free((char *)oline);
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}
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draw_dith(ocm) /* quantize with dithering */
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colormap ocm; /* colormap for orig */
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{
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register int *p,*q,rr,gg,bb,v,x,y,*P,*Q,*R;
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int *buf;
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rgbpixel *iline; /* input scanline */
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pixel *oline; /* output scanline */
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buf = (int *)ecalloc(2,3*sizeof(int)*(xmax+1));
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iline = line3alloc(xmax);
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oline = linealloc(xmax);
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/* reuse hist array as quantization table */
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for (v=0; v<len; v++) hist[v] = -1;
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P = &buf[0];
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Q = &buf[3*(xmax+1)];
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for (y=0; y<ymax; y++, R=P, P=Q, Q=R) {
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Q[0] = Q[1] = Q[2] = 0;
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picreadline3(y,iline);
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for (p=P, q=Q, x=0; x<xmax; x++, p+=3, q+=3) {
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rr = ocm[0][iline[x].r]+p[0];
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gg = ocm[1][iline[x].g]+p[1]; /* ideal */
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bb = ocm[2][iline[x].b]+p[2];
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if (rr<0) rr = 0; else if (rr>255) rr = 255;
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if (gg<0) gg = 0; else if (gg>255) gg = 255;
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if (bb<0) bb = 0; else if (bb>255) bb = 255;
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v = (rr&0xf8)<<7 | (gg&0xf8)<<2 | (bb&0xf8)>>3;
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if (hist[v]<0)
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hist[v] = closest(rr,gg,bb); /* nearest to ideal */
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oline[x] = v = hist[v];
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rr -= color[0][v];
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gg -= color[1][v]; /* error */
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bb -= color[2][v];
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v = rr*3>>3; p[3] += v; q[0] += v; q[3] = rr-(v<<1);
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v = gg*3>>3; p[4] += v; q[1] += v; q[4] = gg-(v<<1);
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v = bb*3>>3; p[5] += v; q[2] += v; q[5] = bb-(v<<1);
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}
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picwriteline(y,oline);
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}
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free((char *)iline);
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free((char *)oline);
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free((char *)buf);
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}
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