add encodeData() to SkImageEncoder, and add encoding to SkImage

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 "SkRefCnt.h"
 #include "SkScalar.h"
 
 class SkData;
 class SkCanvas;
 class SkPaint;
 class SkShader;
 class GrContext;
 class GrTexture;
 
 // need for TileMode
 #include "SkShader.h"
 
-////// EXPERIMENTAL
-
 /**
  *  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
  *  into another canvas.
  *
  *  The content of SkImage is always immutable, though the actual storage may
  *  change, if for example that image can be re-created via encoded data or
  *  other means.
  */
@@ skipping 41 matching lines @@
      * does not affect the reference count of the GrTexture object.
      * Will return NULL if the image does not use a texture.
      */
     GrTexture* getTexture();
 
     SkShader*   newShaderClamp() const;
     SkShader*   newShader(SkShader::TileMode, SkShader::TileMode) const;
 
     void draw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*);
 
+    enum EncodeType {
+        kPNG_EncodeType,

[scroggo, 2013/05/16 17:34:41]

Any reason we don't support all types in SkImageEncoder?

[reed1, 2013/05/16 17:55:02]

Laziness. At first I tried to include SkImageEncoder.h and use its types
directly, but ran into lots of hurt. I'll add more types.

Why the heck can't we take a string or something, so we don't need an enum that
might not reflect new codecs...

+        kJPEG_EncodeType,
+    };
+    /**
+     *  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.
+     */
+    SkData* encode(EncodeType t = kPNG_EncodeType, int quality = 80) const;
+
 protected:
     SkImage(int width, int height) :
         fWidth(width),
         fHeight(height),
         fUniqueID(NextUniqueID()) {
 
         SkASSERT(width >= 0);
         SkASSERT(height >= 0);
     }
 
 private:
     const int       fWidth;
     const int       fHeight;
     const uint32_t  fUniqueID;
 
     static uint32_t NextUniqueID();
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif