Add an option to create unpremultiplied bitmaps.

src/core/SkColor.cpp

Index: src/core/SkColor.cpp
diff --git a/src/core/SkColor.cpp b/src/core/SkColor.cpp
index 6fa239ff539399eb0b061348ee0f0170f014cd97..1133e53f2538d2cac83b467fd2cd8a05709c837f 100644
--- a/src/core/SkColor.cpp
+++ b/src/core/SkColor.cpp
@@ -19,6 +19,18 @@ SkPMColor SkPreMultiplyColor(SkColor c) {
                                    SkColorGetG(c), SkColorGetB(c));
 }
 
+/**
+ *  Interprets c as an unpremultiplied color, and returns the
+ *  premultiplied equivalent.
+ */
+SkPMColor SkPreMultiplyUnPMColor(SkPMColor c) {

[reed1, 2013/06/13 19:33:07]

Since there is no header for this method, and it is pretty trivial (and there is
only one correct way to impl it), I propose we just copy/paste it into the two
testing/sample files that use it for now.

[scroggo, 2013/06/13 20:10:40]

Done.

+    U8CPU a = SkGetPackedA32(c);
+    U8CPU r = SkGetPackedR32(c);
+    U8CPU g = SkGetPackedG32(c);
+    U8CPU b = SkGetPackedB32(c);
+    return SkPreMultiplyARGB(a, r, g, b);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 static inline SkScalar ByteToScalar(U8CPU x) {