commit 73821c8d2bd453de6bf3f516e1f1cdb9a132f4a7
author Chris Craik <ccraik@google.com> Tue Sep 16 17:32:13 2014 -0700
committer Chris Craik <ccraik@google.com> Wed Sep 17 10:00:34 2014 -0700
tree f77d9133dcf359aa2a1933d3894f8bce6a593c60
parent c1e1550bf489b5fafff70154232c24bc5026b7df

Handle premultiplication correctly for ColorMatrixColorFilters

bug:17405627

Previously, the input content to the color matrix computation was left
premultiplied. Since the color matrix could reduce the alpha channel,
the alpha was re-multiplied, but this was incomplete, and incorrect.

Instead, apply the color matrix in unpremultiplied space.

Change-Id: I87b8e03d2e228e6ded81f7bbfea952605d7a095c

libs/hwui/ProgramCache.cpp

diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index a8b8b16..06353c0 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -327,8 +327,10 @@
         // None
         "",
         // Matrix
+        "    fragColor.rgb /= (fragColor.a + 0.0019);\n" // un-premultiply
         "    fragColor *= colorMatrix;\n"
-        "    fragColor += colorMatrixVector;\n",
+        "    fragColor += colorMatrixVector;\n"
+        "    fragColor.rgb *= (fragColor.a + 0.0019);\n", // re-premultiply
         // PorterDuff
         "    fragColor = blendColors(colorBlend, fragColor);\n"
 };