Make SkBlurImageFilter capable of cropping during blur (GPU path).

This is the GPU equivalent of https://codereview.chromium.org/1415653003/.

It requires passing down the bounds of the crop rect (srcBounds), and
turning the blur 3-patch optimization in convolve_gaussian() into a 5-patch:
clear above and below srcBounds, blur with bounds checks inside left and
right rects, blur without bounds checks in middle rect.

Note: this change causes minor pixels diffs in the
imagefilterscropexpand GM: for odd crop positions relative to the
dstBounds, we are now correctly resampling at an even pixel boundary.

BUG=skia:4502, skia:4526

Committed: https://skia.googlesource.com/skia/+/c57e0ded7d535523cfc6bf07c78e5f3479bb8c42

Review URL: https://codereview.chromium.org/1431593002

1 files changed, 5 insertions, 5 deletions

diff --git a/src/effects/SkGpuBlurUtils.h b/src/effects/SkGpuBlurUtils.h
index 357a0d729c..84e3252cc2 100644
--- a/src/effects/SkGpuBlurUtils.h
+++ b/src/effects/SkGpuBlurUtils.h
@@ -26,9 +26,9 @@ namespace SkGpuBlurUtils {
     * @param srcTexture      The source texture to be blurred.
     * @param canClobberSrc   If true, srcTexture may be overwritten, and
     *                        may be returned as the result.
-    * @param rect            The destination rectangle.
-    * @param cropToRect      If true, do not sample any pixels outside the
-    *                        source rect.
+    * @param dstBounds       The destination bounds, relative to the source texture.
+    * @param srcBounds       The source bounds, relative to the source texture. If non-null,
+    *                        no pixels will be sampled outside of this rectangle.
     * @param sigmaX          The blur's standard deviation in X.
     * @param sigmaY          The blur's standard deviation in Y.
     * @return the blurred texture, which may be srcTexture reffed, or a
@@ -37,8 +37,8 @@ namespace SkGpuBlurUtils {
     GrTexture* GaussianBlur(GrContext* context,
                             GrTexture* srcTexture,
                             bool canClobberSrc,
-                            const SkRect& rect,
-                            bool cropToRect,
+                            const SkRect& dstBounds,
+                            const SkRect* srcBounds,
                             float sigmaX,
                             float sigmaY,
                             GrTextureProvider::SizeConstraint);