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[imagemagick] / MagickCore / composite-private.h

diff --git a/MagickCore/composite-private.h b/MagickCore/composite-private.h
index cf9bca64feab21b21d1c40128ca1235f19049e58..d963a7f7c01e76d9358dc62f43563cddd7e0dd00 100644 (file)
--- a/MagickCore/composite-private.h
+++ b/MagickCore/composite-private.h
@@ -32,8 +32,8 @@ extern "C" {
 /*
   ImageMagick Alpha Composite Inline Methods (special export)
 */
-static inline double MagickOver_(const double p,
-  const double alpha,const double q,const double beta)
+static inline double MagickOver_(const double p,const double alpha,
+  const double q,const double beta)
 {
   double
     Da,
@@ -41,7 +41,12 @@ static inline double MagickOver_(const double p,
 
   Sa=QuantumScale*alpha;
   Da=QuantumScale*beta;
-  return(Sa*p-Sa*Da*q+Da*q);
+  return(Sa*p+Da*q*(1.0-Sa));
+}
+
+static inline double RoundToUnity(const double value)
+{
+  return(value < 0.0 ? 0.0 : (value > 1.0) ? 1.0 : value);
 }
 
 static inline void CompositePixelOver(const Image *image,const PixelInfo *p,
@@ -49,6 +54,7 @@ static inline void CompositePixelOver(const Image *image,const PixelInfo *p,
 {
   double
     Da,
+    gamma,
     Sa;
 
   register ssize_t
@@ -59,6 +65,8 @@ static inline void CompositePixelOver(const Image *image,const PixelInfo *p,
   */
   Sa=QuantumScale*alpha;
   Da=QuantumScale*beta;
+  gamma=Sa+Da-Sa*Da;
+  gamma=PerceptibleReciprocal(gamma);
   for (i=0; i < (ssize_t) GetPixelChannels(image); i++)
   {
     PixelChannel
@@ -75,31 +83,31 @@ static inline void CompositePixelOver(const Image *image,const PixelInfo *p,
     {
       case RedPixelChannel:
       {
-        composite[i]=ClampToQuantum(MagickOver_((double) p->red,alpha,
+        composite[i]=ClampToQuantum(gamma*MagickOver_((double) p->red,alpha,
           (double) q[i],beta));
         break;
       }
       case GreenPixelChannel:
       {
-        composite[i]=ClampToQuantum(MagickOver_((double) p->green,alpha,
+        composite[i]=ClampToQuantum(gamma*MagickOver_((double) p->green,alpha,
           (double) q[i],beta));
         break;
       }
       case BluePixelChannel:
       {
-        composite[i]=ClampToQuantum(MagickOver_((double) p->blue,alpha,
+        composite[i]=ClampToQuantum(gamma*MagickOver_((double) p->blue,alpha,
           (double) q[i],beta));
         break;
       }
       case BlackPixelChannel:
       {
-        composite[i]=ClampToQuantum(MagickOver_((double) p->black,alpha,
+        composite[i]=ClampToQuantum(gamma*MagickOver_((double) p->black,alpha,
           (double) q[i],beta));
         break;
       }
       case AlphaPixelChannel:
       {
-        composite[i]=ClampToQuantum(QuantumRange*(Sa+Da-Sa*-Da));
+        composite[i]=ClampToQuantum(QuantumRange*RoundToUnity(Sa+Da-Sa*Da));
         break;
       }
       default:
@@ -116,6 +124,7 @@ static inline void CompositePixelInfoOver(const PixelInfo *p,
 {
   double
     Da,
+    gamma,
     Sa;
 
   /*
@@ -123,17 +132,14 @@ static inline void CompositePixelInfoOver(const PixelInfo *p,
   */
   Sa=QuantumScale*alpha;
   Da=QuantumScale*beta,
-  composite->alpha=(double) QuantumRange*(Sa+Da-Sa*Da);
-  composite->red=MagickOver_(p->red,alpha,q->red,beta);
-  composite->green=MagickOver_(p->green,alpha,q->green,beta);
-  composite->blue=MagickOver_(p->blue,alpha,q->blue,beta);
+  gamma=Sa+Da-Sa*Da;
+  composite->alpha=(double) QuantumRange*RoundToUnity(gamma);
+  gamma=PerceptibleReciprocal(gamma);
+  composite->red=gamma*MagickOver_(p->red,alpha,q->red,beta);
+  composite->green=gamma*MagickOver_(p->green,alpha,q->green,beta);
+  composite->blue=gamma*MagickOver_(p->blue,alpha,q->blue,beta);
   if (q->colorspace == CMYKColorspace)
-    composite->black=MagickOver_(p->black,alpha,q->black,beta);
-}
-
-static inline double RoundToUnity(const double value)
-{
-  return(value < 0.0 ? 0.0 : (value > 1.0) ? 1.0 : value);
+    composite->black=gamma*MagickOver_(p->black,alpha,q->black,beta);
 }
 
 static inline void CompositePixelInfoPlus(const PixelInfo *p,
@@ -150,7 +156,7 @@ static inline void CompositePixelInfoPlus(const PixelInfo *p,
   Sa=QuantumScale*alpha;
   Da=QuantumScale*beta;
   gamma=RoundToUnity(Sa+Da);  /* 'Plus' blending -- not 'Over' blending */
-  composite->alpha=(double) QuantumRange*gamma;
+  composite->alpha=(double) QuantumRange*RoundToUnity(gamma);
   gamma=PerceptibleReciprocal(gamma);
   composite->red=gamma*(Sa*p->red+Da*q->red);
   composite->green=gamma*(Sa*p->green+Da*q->green);