Improve dithering of alpha gradients
Bug: 32984164
Test: CtsUiRenderingTestCases
Change-Id: Ic728725845befd3c52cc7b043d5c6f8e33fcfcd2
diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index 40ab778..3f842e0 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -190,7 +190,7 @@
// Dithering must be done in the quantization space
// When we are writing to an sRGB framebuffer, we must do the following:
// EOTF(OETF(color) + dither)
-// The dithering pattern is generated with a triangle noise generator in the range [-0.0,1.0]
+// The dithering pattern is generated with a triangle noise generator in the range [-1.0,1.0]
// TODO: Handle linear fp16 render targets
const char* gFS_Gradient_Functions = R"__SHADER__(
float triangleNoise(const highp vec2 n) {
@@ -203,7 +203,7 @@
const char* gFS_Gradient_Preamble[2] = {
// Linear framebuffer
"\nvec4 dither(const vec4 color) {\n"
- " return vec4(color.rgb + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0), color.a);\n"
+ " return color + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0);\n"
"}\n"
"\nvec4 gammaMix(const vec4 a, const vec4 b, float v) {\n"
" vec4 c = mix(a, b, v);\n"