Implement correct clipping for image filters.

src/effects/SkBlurImageFilter.cpp

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkBlurImageFilter.h"
 #include "SkColorPriv.h"
@@ skipping 218 matching lines @@
 void SkBlurImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
     if (getInput(0)) {
         getInput(0)->computeFastBounds(src, dst);
     } else {
         *dst = src;
     }
 
     dst->outset(SkScalarMul(fSigma.width(), SkIntToScalar(3)),
                 SkScalarMul(fSigma.height(), SkIntToScalar(3)));
 }
+
+bool SkBlurImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
+                                       SkIRect* dst) const {
+    SkIRect bounds = src;
+    if (getInput(0) && !getInput(0)->filterBounds(src, ctm, &bounds)) {
+        return false;
+    }
+    SkVector sigma, localSigma = SkVector::Make(fSigma.width(), fSigma.height());
+    ctm.mapVectors(&sigma, &localSigma, 1);
+    bounds.outset(SkScalarCeilToInt(SkScalarMul(sigma.x(), SkIntToScalar(3))),
+                  SkScalarCeilToInt(SkScalarMul(sigma.y(), SkIntToScalar(3))));
+    *dst = bounds;
+    return true;
+}
+
 bool SkBlurImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
                                        SkBitmap* result, SkIPoint* offset) {
 #if SK_SUPPORT_GPU
     SkBitmap input;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
     if (!SkImageFilterUtils::GetInputResultGPU(getInput(0), proxy, src, ctm, &input, &srcOffset)) {
         return false;
     }
     GrTexture* source = input.getTexture();
     SkIRect rect;
@@ skipping 13 matching lines @@
                                                              SkRect::Make(rect),
                                                              true,
                                                              sigma.x(),
                                                              sigma.y()));
     return SkImageFilterUtils::WrapTexture(tex, rect.width(), rect.height(), result);
 #else
     SkDEBUGFAIL("Should not call in GPU-less build");
     return false;
 #endif
 }