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diff --git a/MagickCore/colorspace.c b/MagickCore/colorspace.c
index 6ebf51122e326e4c1686485043e22422027988a7..26b73d7ff9291fd7696b59773b1b4bd8eb86d27a 100644 (file)
--- a/MagickCore/colorspace.c
+++ b/MagickCore/colorspace.c
@@ -146,43 +146,40 @@ static inline void ConvertRGBToXYZ(const Quantum red,const Quantum green,
   *Z=0.0139322*r+0.0971045*g+0.7141733*b;
 }
 
-static double LabF1(double alpha)
-{
-
-  if (alpha <= ((24.0/116.0)*(24.0/116.0)*(24.0/116.0)))
-    return((841.0/108.0)*alpha+(16.0/116.0));
-  return(pow(alpha,1.0/3.0));
-}
-
 static inline void ConvertXYZToLab(const double X,const double Y,const double Z,
   double *L,double *a,double *b)
 {
-#define D50X  (0.9642)
+#define D50X  (0.964221)
 #define D50Y  (1.0)
-#define D50Z  (0.8249)
+#define D50Z  (0.825211)
+#define CIEEpsilon  (216.0/24389.0)
+#define CIEK  (24389.0/27.0)
 
   double
-    fx,
-    fy,
-    fz;
+    x,
+    y,
+    z;
 
   assert(L != (double *) NULL);
   assert(a != (double *) NULL);
   assert(b != (double *) NULL);
-  *L=0.0;
-  *a=0.5;
-  *b=0.5;
-  if ((fabs(X) < MagickEpsilon) && (fabs(Y) < MagickEpsilon) &&
-      (fabs(Z) < MagickEpsilon))
-    return;
-  fx=LabF1(X/D50X);
-  fy=LabF1(Y/D50Y);
-  fz=LabF1(Z/D50Z);
-  *L=(116.0*fy-16.0)/100.0;
-  *a=(500.0*(fx-fy))/255.0;
+  if ((X/D50X) > CIEEpsilon)
+    x=pow(X/D50X,1.0/3.0);
+  else
+    x=(CIEK*X/D50X+16.0)/116.0;
+  if ((Y/D50Y) > CIEEpsilon)
+    y=pow(Y/D50Y,1.0/3.0);
+  else
+    y=(CIEK*Y/D50Y+16.0)/116.0;
+  if ((Z/D50Z) > CIEEpsilon)
+    z=pow(Z/D50Z,1.0/3.0);
+  else
+    z=(CIEK*Z/D50Z+16.0)/116.0;
+  *L=((116.0*y)-16.0)/100.0;
+  *a=(500.0*(x-y))/255.0;
   if (*a < 0.0)
     *a+=1.0;
-  *b=(200.0*(fy-fz))/255.0;
+  *b=(200.0*(y-z))/255.0;
   if (*b < 0.0)
     *b+=1.0;
 }
@@ -1253,7 +1250,7 @@ MagickExport MagickBooleanType SetImageColorspace(Image *image,
   image->colorspace=colorspace;
   image->rendering_intent=UndefinedIntent;
   image->gamma=1.000f;
-  ResetMagickMemory(&image->chromaticity,0,sizeof(image->chromaticity));
+  (void) ResetMagickMemory(&image->chromaticity,0,sizeof(image->chromaticity));
   if (IssRGBColorspace(colorspace) != MagickFalse)
     {
       image->rendering_intent=PerceptualIntent;
@@ -1370,19 +1367,6 @@ MagickExport MagickBooleanType TransformImageColorspace(Image *image,
 %
 */
 
-static double LabF2(double alpha)
-{
-  double
-    beta;
-
-  if (alpha > (24.0/116.0))
-    return(alpha*alpha*alpha);
-  beta=(108.0/841.0)*(alpha-(16.0/116.0));
-  if (beta > 0.0)
-    return(beta);
-  return(0.0);
-}
-
 static inline void ConvertLabToXYZ(const double L,const double a,const double b,
   double *X,double *Y,double *Z)
 {
@@ -1394,17 +1378,24 @@ static inline void ConvertLabToXYZ(const double L,const double a,const double b,
   assert(X != (double *) NULL);
   assert(Y != (double *) NULL);
   assert(Z != (double *) NULL);
-  *X=0.0;
-  *Y=0.0;
-  *Z=0.0;
-  if (L <= 0.0)
-    return;
   y=(100.0*L+16.0)/116.0;
-  x=y+255.0*0.002*(a > 0.5 ? a-1.0 : a);
-  z=y-255.0*0.005*(b > 0.5 ? b-1.0 : b);
-  *X=D50X*LabF2(x);
-  *Y=D50Y*LabF2(y);
-  *Z=D50Z*LabF2(z);
+  x=y+255.0*(a > 0.5 ? a-1.0 : a)/500.0;
+  z=y-255.0*(b > 0.5 ? b-1.0 : b)/200.0;
+  if (pow(x,3.0) > CIEEpsilon)
+    x=pow(x,3.0);
+  else
+    x=(116.0*x-16.0)/CIEK;
+  if (pow(y,3.0) > CIEEpsilon)
+    y=pow(y,3.0);
+  else
+    y=L/CIEK;
+  if (pow(z,3.0) > CIEEpsilon)
+    z=pow(z,3.0);
+  else
+    z=(116*z-16.0)/CIEK;
+  *X=D50X*x;
+  *Y=D50Y*y;
+  *Z=D50Z*z;
 }
 
 static inline ssize_t RoundToYCC(const MagickRealType value)
@@ -1463,9 +1454,6 @@ static inline void ConvertCMYKToRGB(PixelInfo *pixel)
 static MagickBooleanType TransformsRGBImage(Image *image,
   const ColorspaceType colorspace,ExceptionInfo *exception)
 {
-#define D50X  (0.9642)
-#define D50Y  (1.0)
-#define D50Z  (0.8249)
 #define TransformsRGBImageTag  "Transform/Image"
 
 #if !defined(MAGICKCORE_HDRI_SUPPORT)