commit 8f2b7fa61765efcaf0a071aabe1db6c59122ab24
author Ben Wagner <bungeman@google.com> Mon May 14 11:14:26 2018 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Mon May 14 16:59:29 2018 +0000
tree da0a52d64594e871fa71465d5538bdd02c91d0b8
parent 0e6db75eebab430e7f6665c8cfa1e7dcd2fef123

Correctly handle empty outer blurs.

Most blur styles approach the original mask as the sigma goes to zero.
The outer style however approaches nothing as the mask sigma goes to
zero. Handle this case correctly.

Change-Id: I14f76e144d7cfc78aeaff30ff5444a21f1e5f98b
Reviewed-on: https://skia-review.googlesource.com/128006
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>

src/core/SkBlurMask.cpp

diff --git a/src/core/SkBlurMask.cpp b/src/core/SkBlurMask.cpp
index f4fa100..0e0d261 100644
--- a/src/core/SkBlurMask.cpp
+++ b/src/core/SkBlurMask.cpp
@@ -110,9 +110,17 @@
         return false;
     }
 
-
     SkMaskBlurFilter blurFilter{sigma, sigma};
-    if (blurFilter.hasNoBlur() && style != kOuter_SkBlurStyle) {
+    if (blurFilter.hasNoBlur()) {
+        // If there is no effective blur most styles will just produce the original mask.
+        // However, kOuter_SkBlurStyle will produce an empty mask.
+        if (style == kOuter_SkBlurStyle) {
+            dst->fImage = nullptr;
+            dst->fBounds = SkIRect::MakeEmpty();
+            dst->fRowBytes = dst->fBounds.width();
+            dst->fFormat = SkMask::kA8_Format;
+            return true;
+        }
         return false;
     }
     const SkIPoint border = blurFilter.blur(src, dst);

src/core/SkMaskBlurFilter.cpp

diff --git a/src/core/SkMaskBlurFilter.cpp b/src/core/SkMaskBlurFilter.cpp
index 7674bdd..ea3d8ab 100644
--- a/src/core/SkMaskBlurFilter.cpp
+++ b/src/core/SkMaskBlurFilter.cpp
@@ -882,8 +882,9 @@
 }
 
 static SkIPoint small_blur(double sigmaX, double sigmaY, const SkMask& src, SkMask* dst) {
-    SkASSERT(0 <= sigmaX && sigmaX < 2);
-    SkASSERT(0 <= sigmaY && sigmaY < 2);
+    SkASSERT(sigmaX == sigmaY); // TODO
+    SkASSERT(0.01 <= sigmaX && sigmaX < 2);
+    SkASSERT(0.01 <= sigmaY && sigmaY < 2);
 
     SkGaussFilter filterX{sigmaX, SkGaussFilter::Type::Bessel},
                   filterY{sigmaY, SkGaussFilter::Type::Bessel};