From bc856c23773e74e9ff056dd62d405d557bd563bd Mon Sep 17 00:00:00 2001
From: Ingo <heckflosse@i-weyrich.de>
Date: Wed, 28 Jan 2015 13:18:01 +0100
Subject: [PATCH] Division by zero in ciecam02, Issue 2646

---
 rtengine/colortemp.cc         | 1 +
 rtengine/improccoordinator.cc | 4 ++--
 rtengine/improcfun.cc         | 9 +++++----
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/rtengine/colortemp.cc b/rtengine/colortemp.cc
index 92c6f2446..268915ee8 100644
--- a/rtengine/colortemp.cc
+++ b/rtengine/colortemp.cc
@@ -2131,6 +2131,7 @@ void ColorTemp::xyz2jchqms_ciecam02float( float &J, float &C, float &h, float &Q
 	Q = wh * J;
 	J *= J * 100.0f;
     M = C * pfl;
+	Q = (Q == 0.f ? 0.0001f : Q); // avoid division by zero
     s = 100.0f * sqrtf( M / Q );
     h = (myh * 180.f) / (float)M_PI;
 
diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index c805d240e..cb25ec8ee 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -620,9 +620,9 @@ void ImProcCoordinator::updatePreviewImage (int todo, Crop* cropCall) {
                 ncie = new CieImage (pW, pH);
 
             if (!CAMBrightCurveJ && (params.colorappearance.algo=="JC" || params.colorappearance.algo=="JS" || params.colorappearance.algo=="ALL"))
-                CAMBrightCurveJ(65536,0);
+                CAMBrightCurveJ(32768,0);
             if (!CAMBrightCurveQ && (params.colorappearance.algo=="QM" || params.colorappearance.algo=="ALL"))
-                CAMBrightCurveQ(65536,0);
+                CAMBrightCurveQ(32768,0);
             if(settings->ciecamfloat){
                 ipf.ciecam_02float (ncie, float(adap), begh, endh, pW, 2, nprevl, &params, customColCurve1,customColCurve2,customColCurve3, histLCAM, histCCAM, CAMBrightCurveJ, CAMBrightCurveQ, CAMMean, 5, 1, execsharp, d, scale, 1);
                 if(params.colorappearance.autodegree && acListener && params.colorappearance.enabled) acListener->autoCamChanged(100.*(double)d);
diff --git a/rtengine/improcfun.cc b/rtengine/improcfun.cc
index b223251dd..f54be0903 100644
--- a/rtengine/improcfun.cc
+++ b/rtengine/improcfun.cc
@@ -1365,7 +1365,7 @@ if(params->colorappearance.enabled) {
 		//evaluate lightness, contrast
 		if (needJ) {
 			if (!CAMBrightCurveJ) {
-				CAMBrightCurveJ(65536,0);
+				CAMBrightCurveJ(32768,0);
 				CAMBrightCurveJ.dirty = false;
 			}
 			float jli=params->colorappearance.jlight;
@@ -1374,7 +1374,7 @@ if(params->colorappearance.enabled) {
 		}
 		if (needQ) {
 			if (!CAMBrightCurveQ) {
-				CAMBrightCurveQ(65536,0);
+				CAMBrightCurveQ(32768,0);
 				CAMBrightCurveQ.clear();
 				CAMBrightCurveQ.dirty = false;
 			}
@@ -1497,8 +1497,8 @@ if(settings->viewinggreySc==1) yb=18.0f;//fixed
 			else if(alg==3 || alg==0  || alg==2) {
 				if(alg==3 || alg==2) {
 					float coef=32760.f/wh;
-					if(Qpro*coef > 32767.0f)
-						Qpro=(CAMBrightCurveQ[(float)32767.0f])/coef;//brightness and contrast
+					if(Qpro*coef >= 32767.0f)
+						Qpro=(CAMBrightCurveQ[32767])/coef;//brightness and contrast
 					else
 						Qpro=(CAMBrightCurveQ[(float)(Qpro*coef)])/coef;//brightness and contrast
 				}
@@ -1512,6 +1512,7 @@ if(settings->viewinggreySc==1) yb=18.0f;//fixed
 				Color::skinredfloat(Jpro, hpro, sres, Mp, dred, protect_red,0,rstprotection,100.f, Mpro);
 				Jpro = SQR((10.f*Qpro)/wh);
 				Cpro= Mpro/coe;
+				Qpro = (Qpro == 0.f ? epsil : Qpro); // avoid division by zero
 				spro = 100.0f * sqrtf( Mpro / Qpro );
 				if(alg!=2) {
 					if(Jpro > 99.9f)