Fix alpha channel computation with ColorMatrixColorFilter

Bug #7222476

There were two issues:
- Blending was ignored with color filters
- The addition vector of a color filter was treated as integer values
  instead of float values

Change-Id: Id94065704a30ee8aaaa5724a9f3a3cff7c50ced7

Author: Romain Guy

libs/hwui/OpenGLRenderer.cpp

@@ -1398,8 +1398,8 @@ void OpenGLRenderer::setupDrawBlending(bool blend, SkXfermode::Mode mode, bool s
     // When the blending mode is kClear_Mode, we need to use a modulate color
     // argb=1,0,0,0
     accountForClear(mode);
-    chooseBlending(blend || (mColorSet && mColorA < 1.0f) || (mShader && mShader->blend()), mode,
-            mDescription, swapSrcDst);
+    chooseBlending(blend || (mColorSet && mColorA < 1.0f) || (mShader && mShader->blend()) ||
+            (mColorFilter && mColorFilter->blend()), mode, mDescription, swapSrcDst);
 }
 
 void OpenGLRenderer::setupDrawProgram() {

libs/hwui/ProgramCache.cpp

@@ -347,7 +347,6 @@ const char* gFS_Main_ApplyColorOp[4] = {
         // None
         "",
         // Matrix
-        // TODO: Fix premultiplied alpha computations for color matrix
         "    fragColor *= colorMatrix;\n"
         "    fragColor += colorMatrixVector;\n"
         "    fragColor.rgb *= fragColor.a;\n",

libs/hwui/SkiaColorFilter.cpp

@@ -34,13 +34,10 @@ SkiaColorFilter::~SkiaColorFilter() {
 // Color matrix filter
 ///////////////////////////////////////////////////////////////////////////////
 
-SkiaColorMatrixFilter::SkiaColorMatrixFilter(SkColorFilter *skFilter, float* matrix, float* vector):
+SkiaColorMatrixFilter::SkiaColorMatrixFilter(SkColorFilter* skFilter, float* matrix, float* vector):
         SkiaColorFilter(skFilter, kColorMatrix, true), mMatrix(matrix), mVector(vector) {
-    // Skia uses the range [0..255] for the addition vector, but we need
-    // the [0..1] range to apply the vector in GLSL
-    for (int i = 0; i < 4; i++) {
-        mVector[i] /= 255.0f;
-    }
+    // TODO: We should be smarter about this
+    mBlend = true;
 }
 
 SkiaColorMatrixFilter::~SkiaColorMatrixFilter() {
@@ -62,7 +59,7 @@ void SkiaColorMatrixFilter::setupProgram(Program* program) {
 // Lighting color filter
 ///////////////////////////////////////////////////////////////////////////////
 
-SkiaLightingFilter::SkiaLightingFilter(SkColorFilter *skFilter, int multiply, int add):
+SkiaLightingFilter::SkiaLightingFilter(SkColorFilter* skFilter, int multiply, int add):
         SkiaColorFilter(skFilter, kLighting, true) {
     mMulR = ((multiply >> 16) & 0xFF) / 255.0f;
     mMulG = ((multiply >>  8) & 0xFF) / 255.0f;
@@ -71,6 +68,9 @@ SkiaLightingFilter::SkiaLightingFilter(SkColorFilter *skFilter, int multiply, in
     mAddR = ((add >> 16) & 0xFF) / 255.0f;
     mAddG = ((add >>  8) & 0xFF) / 255.0f;
     mAddB = ((add      ) & 0xFF) / 255.0f;
+
+    // A lighting filter always ignores alpha
+    mBlend = false;
 }
 
 void SkiaLightingFilter::describe(ProgramDescription& description, const Extensions& extensions) {
@@ -86,13 +86,16 @@ void SkiaLightingFilter::setupProgram(Program* program) {
 // Blend color filter
 ///////////////////////////////////////////////////////////////////////////////
 
-SkiaBlendFilter::SkiaBlendFilter(SkColorFilter *skFilter, int color, SkXfermode::Mode mode):
+SkiaBlendFilter::SkiaBlendFilter(SkColorFilter* skFilter, int color, SkXfermode::Mode mode):
         SkiaColorFilter(skFilter, kBlend, true), mMode(mode) {
     const int alpha = (color >> 24) & 0xFF;
     mA = alpha / 255.0f;
     mR = mA * ((color >> 16) & 0xFF) / 255.0f;
     mG = mA * ((color >>  8) & 0xFF) / 255.0f;
     mB = mA * ((color      ) & 0xFF) / 255.0f;
+
+    // TODO: We should do something smarter here
+    mBlend = true;
 }
 
 void SkiaBlendFilter::describe(ProgramDescription& description, const Extensions& extensions) {