Fix fast blur for shadow rrects.

* Handles case where blur is greater than
  corner radius.
* Speeds up shader by avoiding a divide.
* Tweaks shadow sample to be more MD-ish.

Bug: skia:
Change-Id: I2990357b39784c22f02a8e51872391fd68e8226a
Reviewed-on: https://skia-review.googlesource.com/14141
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/utils/SkShadowTessellator.cpp b/src/utils/SkShadowTessellator.cpp
index 7d29b063a0..5dee5df3e0 100755
--- a/src/utils/SkShadowTessellator.cpp
+++ b/src/utils/SkShadowTessellator.cpp
@@ -778,7 +778,7 @@ SkSpotShadowTessellator::SkSpotShadowTessellator(const SkPath& path, const SkMat
         // if the umbra would collapse, we back off a bit on inner blur and adjust the alpha
         SkScalar newRadius = SkScalarSqrt(minDistSq) - kTolerance;
         fOffsetAdjust = newRadius - radius;
-        SkScalar ratio = 256 * newRadius / radius;
+        SkScalar ratio = 128 * (newRadius + radius) / radius;
         // they aren't PMColors, but the interpolation algorithm is the same
         fUmbraColor = SkPMLerp(fUmbraColor, fPenumbraColor, (unsigned)ratio);
         radius = newRadius;