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/* |
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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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|
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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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|
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#include "ciq.h" |
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|
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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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|
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int hist[len]; /* list of frequencies or pixelvalues for coded color */ |
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|
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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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/*----------------------------------------------------------------------*/ |
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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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|
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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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|
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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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|
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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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|
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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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/*----------------------------------------------------------------------*/ |
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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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|
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line = line3alloc(xmax); |
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convertmap(ocm,map); |
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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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} |
