Fix zero-sized blur with crop rect.

src/effects/SkBlurImageFilter.cpp

Index: src/effects/SkBlurImageFilter.cpp
diff --git a/src/effects/SkBlurImageFilter.cpp b/src/effects/SkBlurImageFilter.cpp
index 5d58369bc765cd561f6836a702145c7b4af0b6f1..631cd35f8c05276afcc35da1d3162cc0e25c997b 100644
--- a/src/effects/SkBlurImageFilter.cpp
+++ b/src/effects/SkBlurImageFilter.cpp
@@ -90,18 +90,6 @@ bool SkBlurImageFilter::onFilterImage(Proxy* proxy,
         return false;
     }
 
-    SkAutoLockPixels alp(src);
-    if (!src.getPixels()) {
-        return false;
-    }
-
-    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(dstBounds.width(), dstBounds.height()));
-    if (!device) {
-        return false;
-    }
-    *dst = device->accessBitmap(false);
-    SkAutoLockPixels alp_dst(*dst);
-
     SkVector sigma = mapSigma(fSigma, ctx.ctm());
 
     int kernelSizeX, kernelSizeX3, lowOffsetX, highOffsetX;
@@ -114,12 +102,24 @@ bool SkBlurImageFilter::onFilterImage(Proxy* proxy,
     }
 
     if (kernelSizeX == 0 && kernelSizeY == 0) {
-        src.copyTo(dst, dst->colorType());
-        offset->fX = dstBounds.x() + srcOffset.x();
-        offset->fY = dstBounds.y() + srcOffset.y();
+        src.extractSubset(dst, srcBounds);
+        offset->fX = srcBounds.x();
+        offset->fY = srcBounds.y();
         return true;
     }
 
+    SkAutoLockPixels alp(src);
+    if (!src.getPixels()) {
+        return false;
+    }
+
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(dstBounds.width(), dstBounds.height()));
+    if (!device) {
+        return false;
+    }
+    *dst = device->accessBitmap(false);
+    SkAutoLockPixels alp_dst(*dst);
+
     SkAutoTUnref<SkBaseDevice> tempDevice(proxy->createDevice(dst->width(), dst->height()));
     if (!tempDevice) {
         return false;
@@ -211,15 +211,21 @@ bool SkBlurImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const
     if (!srcBounds.intersect(dstBounds)) {
         return false;
     }
-    GrTexture* source = input.getTexture();
     SkVector sigma = mapSigma(fSigma, ctx.ctm());

[robertphillips, 2016/02/01 17:41:35]

Do we need/want an epsilon-based comparison here ?

[Stephen White, 2016/02/01 18:20:03]

Since GaussianBlur() does exact comparisons as well (and only
does the wrong thing when they're exactly zero), it should be
safe to do here as well.

+    if (sigma.x() == 0 && sigma.y() == 0) {
+        input.extractSubset(result, srcBounds);
+        offset->fX = srcBounds.x();
+        offset->fY = srcBounds.y();
+        return true;
+    }
     offset->fX = dstBounds.fLeft;
     offset->fY = dstBounds.fTop;
     srcBounds.offset(-srcOffset);
     dstBounds.offset(-srcOffset);
     SkRect srcBoundsF(SkRect::Make(srcBounds));
-    SkAutoTUnref<GrTexture> tex(SkGpuBlurUtils::GaussianBlur(source->getContext(),
-                                                             source,
+    GrTexture* inputTexture = input.getTexture();
+    SkAutoTUnref<GrTexture> tex(SkGpuBlurUtils::GaussianBlur(inputTexture->getContext(),
+                                                             inputTexture,
                                                              false,
                                                              SkRect::Make(dstBounds),
                                                              &srcBoundsF,