1 files changed, 47 insertions, 0 deletions
diff --git a/skia/include/SkUnPreMultiply.h b/skia/include/SkUnPreMultiply.h
new file mode 100644
index 0000000..bbbcea1
--- /dev/null
+++ b/skia/include/SkUnPreMultiply.h
@@ -0,0 +1,47 @@
+
+
+
+#ifndef SkUnPreMultiply_DEFINED
+#define SkUnPreMultiply_DEFINED
+
+#include "SkColor.h"
+
+class SkUnPreMultiply {
+public:
+    typedef uint32_t Scale;
+    
+    // index this table with alpha [0..255]
+    static const Scale* GetScaleTable() {
+        return gTable;
+    }
+
+    static Scale GetScale(U8CPU alpha) {
+        SkASSERT(alpha <= 255);
+        return gTable[alpha];
+    }
+    
+    /** Usage:
+     
+        const Scale* table = SkUnPreMultiply::GetScaleTable();
+     
+        for (...) {
+            unsigned a = ...
+            SkUnPreMultiply::Scale scale = table[a];
+     
+            red = SkUnPreMultiply::ApplyScale(scale, red);
+            ...
+            // now red is unpremultiplied
+        }
+    */
+    static U8CPU ApplyScale(Scale scale, U8CPU component) {
+        SkASSERT(component <= 255);
+        return (scale * component + (1 << 23)) >> 24;
+    }
+    
+    static SkColor PMColorToColor(SkPMColor c);
+    
+private:
+    static const uint32_t gTable[256];
+};
+
+#endif