--- ray/src/common/ccolor.c	2015/04/05 01:32:01	3.8
+++ ray/src/common/ccolor.c	2016/01/23 18:58:35	3.9
@@ -1,14 +1,18 @@
 #ifndef lint
-static const char RCSid[] = "$Id: ccolor.c,v 3.8 2015/04/05 01:32:01 greg Exp $";
+static const char RCSid[] = "$Id: ccolor.c,v 3.9 2016/01/23 18:58:35 greg Exp $";
 #endif
 /*
  * Spectral color handling routines
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <math.h>
 #include "ccolor.h"
 
+#undef frand
+#define frand()	(rand()*(1./(RAND_MAX+.5)))
+
 					/* Sharp primary matrix */
 float	XYZtoSharp[3][3] = {
 	{ 1.2694, -0.0988, -0.1706},
@@ -24,6 +28,8 @@ float	XYZfromSharp[3][3] = {
 
 const C_COLOR	c_dfcolor = C_DEFCOLOR;
 
+const C_CHROMA	c_dfchroma = 49750;	/* c_encodeChroma(&c_dfcolor) */
+
 				/* CIE 1931 Standard Observer curves */
 const C_COLOR	c_x31 = { 1, NULL, C_CDSPEC|C_CSSPEC|C_CSXY|C_CSEFF,
 			{14,42,143,435,1344,2839,3483,3362,2908,1954,956,
@@ -183,9 +189,9 @@ c_sset(C_COLOR *clr, double wlmin, double wlmax, const
 				pos++;
 			}
 			if ((wl+1e-7 >= wl0) & (wl-1e-7 <= wl0))
-				clr->ssamp[i] = scale*va[pos] + .5;
+				clr->ssamp[i] = scale*va[pos] + frand();
 			else		/* interpolate if necessary */
-				clr->ssamp[i] = .5 + scale / wlstep *
+				clr->ssamp[i] = frand() + scale / wlstep *
 						( va[pos]*(wl0+wlstep - wl) +
 							va[pos+1]*(wl - wl0) );
 			clr->ssum += clr->ssamp[i];
@@ -243,7 +249,7 @@ c_ccvt(C_COLOR *clr, int fl)
 		clr->ssum = 0;
 		for (i = 0; i < C_CNSS; i++) {
 			clr->ssamp[i] = x*cie_xp.ssamp[i] + y*cie_yp.ssamp[i]
-					+ z*cie_zp.ssamp[i] + .5;
+					+ z*cie_zp.ssamp[i] + frand();
 			if (clr->ssamp[i] < 0)		/* out of gamut! */
 				clr->ssamp[i] = 0;
 			else
@@ -290,7 +296,7 @@ c_cmix(C_COLOR *cres, double w1, C_COLOR *c1, double w
 		scale = C_CMAXV / scale;
 		cres->ssum = 0;
 		for (i = 0; i < C_CNSS; i++)
-			cres->ssum += cres->ssamp[i] = scale*cmix[i] + .5;
+			cres->ssum += cres->ssamp[i] = scale*cmix[i] + frand();
 		cres->flags = C_CDSPEC|C_CSSPEC;
 	} else {					/* CIE xy mixing */
 		c_ccvt(c1, C_CSXY);
@@ -380,7 +386,7 @@ c_bbtemp(C_COLOR *clr, double tk)
 	clr->ssum = 0;
 	for (i = 0; i < C_CNSS; i++) {
 		wl = (C_CMINWL + i*C_CWLI)*1e-9;
-		clr->ssum += clr->ssamp[i] = sf*bbsp(wl,tk) + .5;
+		clr->ssum += clr->ssamp[i] = sf*bbsp(wl,tk) + frand();
 	}
 	clr->flags = C_CDSPEC|C_CSSPEC;
 	return(1);
@@ -402,12 +408,12 @@ c_encodeChroma(C_COLOR *clr)
 
 	c_ccvt(clr, C_CSXY);
 	df = UV_NORMF/(-2.*clr->cx + 12.*clr->cy + 3.);
-	ub = 4.*clr->cx * df;
-	if (ub < 0) ub = 0;
-	else if (ub > 0xff) ub = 0xff;
-	vb = 9.*clr->cy * df;
-	if (vb < 0) vb = 0;
-	else if (vb > 0xff) vb = 0xff;
+	ub = 4.*clr->cx*df + frand();
+	ub *= (ub > 0);
+	if (ub > 0xff) ub = 0xff;
+	vb = 9.*clr->cy*df + frand();
+	vb *= (vb > 0);
+	if (vb > 0xff) vb = 0xff;
 
 	return(vb<<8 | ub);
 }
@@ -416,8 +422,8 @@ c_encodeChroma(C_COLOR *clr)
 void
 c_decodeChroma(C_COLOR *cres, C_CHROMA ccode)
 {
-	double	up = ((ccode & 0xff) + .5)*(1./UV_NORMF);
-	double	vp = ((ccode>>8 & 0xff) + .5)*(1./UV_NORMF);
+	double	up = (ccode & 0xff)*(1./UV_NORMF);
+	double	vp = (ccode>>8 & 0xff)*(1./UV_NORMF);
 	double	df = 1./(6.*up - 16.*vp + 12.);
 
 	cres->cx = 9.*up * df;