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

include/core/SkImage.h

Index: include/core/SkImage.h
diff --git a/include/core/SkImage.h b/include/core/SkImage.h
index e6ac68287672d1582ffde1adc1fc74fc8c8176dc..6a93d3b78b7f0515f625c331964da4fe55d5e057 100644
--- a/include/core/SkImage.h
+++ b/include/core/SkImage.h
@@ -21,8 +21,6 @@ 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
@@ -84,6 +82,19 @@ public:
 
     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),