Image filters: optimize crop rect application

include/core/SkImageFilter.h

Index: include/core/SkImageFilter.h
diff --git a/include/core/SkImageFilter.h b/include/core/SkImageFilter.h
index d1b1483386bdd0c3378a16c50cd27e5e8e649c79..c677c9a297395b16c27b8b9242fc305d97fcfd1e 100644
--- a/include/core/SkImageFilter.h
+++ b/include/core/SkImageFilter.h
@@ -88,12 +88,14 @@ public:
 
         /**
          *  Apply this cropRect to the imageBounds. If a given edge of the cropRect is not
-         *  set, then the corresponding edge from imageBounds will be used.
+         *  set, then the corresponding edge from imageBounds will be used. If "embiggen"
+         *  is false, edges which would grow the size of the bounds will be ignored; only
+         *  edges which reduce the size of the bounds will be used.

[robertphillips, 2016/04/01 19:58:08]

Maybe:
* This is to accommodate filter that affect transparent black. In such cases
(i.e.,
* when embiggen is set) the resulting rect must cover all the pixels

?

[Stephen White, 2016/04/01 21:26:35]

OK, I tried to clarify it a bit.

          *
          *  Note: imageBounds is in "device" space, as the output cropped rectangle will be,
          *  so the matrix is ignored for those. It is only applied the croprect's bounds.
          */

[robertphillips, 2016/04/01 19:58:08]

overlength

[Stephen White, 2016/04/01 21:26:35]

Fixed.

-        void applyTo(const SkIRect& imageBounds, const SkMatrix&, SkIRect* cropped) const;
+        void applyTo(const SkIRect& imageBounds, const SkMatrix&, bool embiggen, SkIRect* dst) const;
 
     private:
         SkRect fRect;
@@ -249,7 +251,7 @@ public:
     virtual SkRect computeFastBounds(const SkRect&) const;
 
     // Can this filter DAG compute the resulting bounds of an object-space rectangle?
-    virtual bool canComputeFastBounds() const;
+    bool canComputeFastBounds() const;
 
     /**
      *  If this filter can be represented by another filter + a localMatrix, return that filter,
@@ -466,6 +468,7 @@ private:
                                SkBitmap* result, SkIPoint* offset) const;
 
     bool usesSrcInput() const { return fUsesSrcInput; }
+    virtual bool affectsTransparentBlack() const { return false; }
 
     typedef SkFlattenable INHERITED;
     int fInputCount;