Make GrGLConfigConversionEffect work on Intel GPUs
BUG=247664
R=noel@chromium.org, bsalomon@chromium.org, reed@google.com, tomhudson@chromium.org, bsalomon@google.com
Author: jun.a.jiang@intel.com
Review URL: https://chromiumcodereview.appspot.com/15719007
git-svn-id: http://skia.googlecode.com/svn/trunk@9672 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrConfigConversionEffect.cpp b/src/gpu/effects/GrConfigConversionEffect.cpp
index 1e65a6f..fd6264f 100644
--- a/src/gpu/effects/GrConfigConversionEffect.cpp
+++ b/src/gpu/effects/GrConfigConversionEffect.cpp
@@ -50,8 +50,12 @@
outputColor, outputColor, swiz, outputColor, outputColor);
break;
case GrConfigConversionEffect::kMulByAlpha_RoundDown_PMConversion:
+ // Add a compensation(0.001) here to avoid the side effect of the floor operation.
+ // In Intel GPUs, the integer value converted from floor(%s.r * 255.0) / 255.0
+ // is less than the integer value converted from %s.r by 1 when the %s.r is
+ // converted from the integer value 2^n, such as 1, 2, 4, 8, etc.
builder->fsCodeAppendf(
- "\t\t%s = vec4(floor(%s.%s * %s.a * 255.0) / 255.0, %s.a);\n",
+ "\t\t%s = vec4(floor(%s.%s * %s.a * 255.0 + 0.001) / 255.0, %s.a);\n",
outputColor, outputColor, swiz, outputColor, outputColor);
break;
case GrConfigConversionEffect::kDivByAlpha_RoundUp_PMConversion: