--- ray/src/px/ciq.c	1989/02/02 14:10:33	1.2
+++ ray/src/px/ciq.c	1991/11/12 16:04:10	2.1
@@ -13,6 +13,7 @@ Paul Heckbert	16 April 82, cleaned up 8 June 86
 Greg Ward	1 March 88, modified for arbitrary picture sizes
 */
 
+#include "standard.h"
 #include "ciq.h"
 
 #define table(m,r,g,b) hist[m[0][r]|m[1][g]|m[2][b]]  /* histogram/pvtable */
@@ -22,6 +23,9 @@ int hist[len];		/* list of frequencies or pixelvalues 
 colormap color;		/* quantization colormap */
 int n;			/* number of colors in it */
 
+#define ERRMAX 20	/* maximum allowed propagated error,
+			   if >=255 then no clamping */
+
 /*----------------------------------------------------------------------*/
 
 ciq(dith,nw,synth,cm)
@@ -40,7 +44,7 @@ colormap cm;		/* quantization colormap */
     if (synth)
 	n = makecm(nw,&na);	/* analyze histogram and synthesize colormap */
     else {
-	bcopy(cm,color,sizeof color);
+	bcopy((char *)cm,(char *)color,sizeof color);
 	n = nw;
 	na = 0;
 	for (i=0; i<len; i++) if (hist[i]) na++;
@@ -48,6 +52,7 @@ colormap cm;		/* quantization colormap */
     }
     picwritecm(color);
 
+    initializeclosest();
     if (dith)
 	draw_dith(ocm);
     else {
@@ -56,7 +61,7 @@ colormap cm;		/* quantization colormap */
 	draw_nodith(ocm);
     }
 
-    bcopy(color,cm,sizeof color);
+    bcopy((char *)color,(char *)cm,sizeof color);
     /*endclosest();*/
 }
 
@@ -70,6 +75,9 @@ colormap ocm;
     rgbpixel *line;
     colormap map;
 
+    for (x = 0; x < len; x++)	/* clear histogram */
+	hist[x] = 0;
+
     line = line3alloc(xmax);
     convertmap(ocm,map);
 
@@ -136,9 +144,16 @@ colormap ocm;			/* colormap for orig */
 	Q[0] = Q[1] = Q[2] = 0;
 	picreadline3(y,iline);
 	for (p=P, q=Q, x=0; x<xmax; x++, p+=3, q+=3) {
-	    rr = ocm[0][iline[x].r]+p[0];
-	    gg = ocm[1][iline[x].g]+p[1];	/* ideal */
-	    bb = ocm[2][iline[x].b]+p[2];
+	    rr = p[0];
+	    if (rr<-ERRMAX) rr = -ERRMAX; else if (rr>ERRMAX) rr = ERRMAX;
+	    gg = p[1];
+	    if (gg<-ERRMAX) gg = -ERRMAX; else if (gg>ERRMAX) gg = ERRMAX;
+	    bb = p[2];
+	    if (bb<-ERRMAX) bb = -ERRMAX; else if (bb>ERRMAX) bb = ERRMAX;
+	    /* now rr,gg,bb is propagated color */
+	    rr += ocm[0][iline[x].r];
+	    gg += ocm[1][iline[x].g];	/* ideal */
+	    bb += ocm[2][iline[x].b];
 	    if (rr<0) rr = 0; else if (rr>255) rr = 255;
 	    if (gg<0) gg = 0; else if (gg>255) gg = 255;
 	    if (bb<0) bb = 0; else if (bb>255) bb = 255;