Image filters: implement SkImage::makeWithFilter().

include/core/SkImage.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_DEFINED
 #define SkImage_DEFINED
 
@@ skipping 302 matching lines @@
      */
     sk_sp<SkImage> makeSubset(const SkIRect& subset) const;
 
     /**
      *  Ensures that an image is backed by a texture (when GrContext is non-null). If no
      *  transformation is required, the returned image may be the same as this image. If the this
      *  image is from a different GrContext, this will fail.
      */
     sk_sp<SkImage> makeTextureImage(GrContext*) const;
 
+    /**
+     *  Apply a given image filter to this image, and return the filtered result.
+     *
+     *  The subset represents the active portion of this image. The return value is similarly an
+     *  Skimage, with an active subset (outSubset). This is usually used with texture-backed
+     *  images, where the texture may be approx-match and thus larger than the required size.
+     *

[robertphillips, 2016/05/19 16:35:19]

Doesn't clipBounds also capture the position - not just the size ?

[Stephen White, 2016/05/19 17:31:26]

Fixed.

+     *  clipBounds represents the maximum size of the image which may be produced.
+     *
+     *  offset is the amount to translate the resulting image relative to the src when it is drawn.
+     *  This is an out-param.
+     *
+     *  If the result image cannot be created, or the result would be transparent black, null

[robertphillips, 2016/05/19 16:35:19]

subset -> outSubset ?

[Stephen White, 2016/05/19 17:31:26]

Done.

+     *  is returned, in which case the offset and subset parameters should be ignored by the caller.
+     */
+    sk_sp<SkImage> makeWithFilter(const SkImageFilter* filter, const SkIRect& subset,
+                                  const SkIRect& clipBounds, SkIRect* outSubset,
+                                  SkIPoint* offset);
+
     /** Drawing params for which a deferred texture image data should be optimized. */
     struct DeferredTextureImageUsageParams {
         SkMatrix        fMatrix;
         SkFilterQuality fQuality;
     };
 
     /**
      * This method allows clients to capture the data necessary to turn a SkImage into a texture-
      * backed image. If the original image is codec-backed this will decode into a format optimized
      * for the context represented by the proxy. This method is thread safe with respect to the
@@ skipping 90 matching lines @@
 
 private:
     const int       fWidth;
     const int       fHeight;
     const uint32_t  fUniqueID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif