Add preserves premul and modulate optimization to compose fragment processors.

Fixes out of range colors produced by matrix convolution and dither effects. Adds modulate optimization to matrix convolution.

Change-Id: I8424250a52e864f4b5feaf4474293695c26039d8
Reviewed-on: https://skia-review.googlesource.com/8351
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index 1a40514c83..fc8add85fd 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -98,6 +98,7 @@ void GrGLMatrixConvolutionEffect::emitCode(EmitArgs& args) {
     }
     if (mce.convolveAlpha()) {
         fragBuilder->codeAppendf("%s = sum * %s + %s;", args.fOutputColor, gain, bias);
+        fragBuilder->codeAppendf("%s.a = clamp(%s.a, 0, 1);", args.fOutputColor, args.fOutputColor);
         fragBuilder->codeAppendf("%s.rgb = clamp(%s.rgb, 0.0, %s.a);",
                                  args.fOutputColor, args.fOutputColor, args.fOutputColor);
     } else {
@@ -109,7 +110,7 @@ void GrGLMatrixConvolutionEffect::emitCode(EmitArgs& args) {
                               coords2D,
                               args.fTexSamplers[0]);
         fragBuilder->codeAppendf("%s.a = c.a;", args.fOutputColor);
-        fragBuilder->codeAppendf("%s.rgb = sum.rgb * %s + %s;", args.fOutputColor, gain, bias);
+        fragBuilder->codeAppendf("%s.rgb = clamp(sum.rgb * %s + %s, 0, 1);", args.fOutputColor, gain, bias);
         fragBuilder->codeAppendf("%s.rgb *= %s.a;", args.fOutputColor, args.fOutputColor);
     }
 
@@ -157,9 +158,8 @@ GrMatrixConvolutionEffect::GrMatrixConvolutionEffect(GrTexture* texture,
                                                      const SkIPoint& kernelOffset,
                                                      GrTextureDomain::Mode tileMode,
                                                      bool convolveAlpha)
-        // To advertise either the modulation or opaqueness optimizations we'd have to examine the
-        // parameters.
-        : INHERITED(texture, nullptr, SkMatrix::I(), kNone_OptimizationFlags)
+        // To advertise the preserves opaqueness optimization we'd have to examine the parameters.
+        : INHERITED(texture, nullptr, SkMatrix::I(), kModulatesInput_OptimizationFlag)
         , fKernelSize(kernelSize)
         , fGain(SkScalarToFloat(gain))
         , fBias(SkScalarToFloat(bias) / 255.0f)