Add a SkPixelSerializer SkImage encode variant

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
 
 #include "SkFilterQuality.h"
 #include "SkImageInfo.h"
 #include "SkImageEncoder.h"
 #include "SkRefCnt.h"
 #include "SkScalar.h"
 #include "SkShader.h"
 
 class SkData;
 class SkCanvas;
 class SkColorTable;
 class SkImageGenerator;
 class SkPaint;
 class SkPicture;
+class SkPixelSerializer;
 class SkString;
 class SkSurface;
 class SkSurfaceProps;
 class GrContext;
 class GrTexture;
 
 /**
  *  SkImage is an abstraction for drawing a rectagle of pixels, though the
  *  particular type of image could be actually storing its data on the GPU, or
  *  as drawing commands (picture or PDF or otherwise), ready to be played back
@@ skipping 193 matching lines @@
                     int srcX, int srcY) const;
 
     bool readPixels(const SkPixmap& dst, int srcX, int srcY) const;
 
     /**
      *  Encode the image's pixels and return the result as a new SkData, which
      *  the caller must manage (i.e. call unref() when they are done).
      *
      *  If the image type cannot be encoded, or the requested encoder type is
      *  not supported, this will return NULL.
+     *
+     *  Note: this will attempt to encode the image's pixels in the specified format,
+     *  even if the image returns a data from refEncoded(). That data will be ignored.
      */
     SkData* encode(SkImageEncoder::Type, int quality) const;
 
-    SkData* encode() const {
-        return this->encode(SkImageEncoder::kPNG_Type, 100);
-    }
+    /**
+     *  Encode the image and return the result as a caller-managed SkData.  This will
+     *  attempt to reuse existing encoded data (as returned by refEncoded).
+     *
+     *  We defer to the SkPixelSerializer both for vetting existing encoded data
+     *  (useEncodedData) and for encoding the image (encodePixels) when no such data is
+     *  present or is rejected by the serializer.
+     *
+     *  If not specified, we use a default serializer which 1) always accepts existing data
+     *  (in any format) and 2) encodes to PNG.
+     *
+     *  If no compatible encoded data exists and encoding fails, this method will also
+     *  fail (return NULL).
+     */
+    SkData* encode(SkPixelSerializer* = nullptr) const;
 
     /**
      *  If the image already has its contents in encoded form (e.g. PNG or JPEG), return a ref
      *  to that data (which the caller must call unref() on). The caller is responsible for calling
      *  unref on the data when they are done.
      *
      *  If the image does not already has its contents in encoded form, return NULL.
      *
      *  Note: to force the image to return its contents as encoded data, try calling encode(...).
      */
@@ skipping 60 matching lines @@
 
 private:
     const int       fWidth;
     const int       fHeight;
     const uint32_t  fUniqueID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif