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

src/image/SkImage.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkImagePriv.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
+#include "../images/SkImageEncoder.h"
 
 SK_DEFINE_INST_COUNT(SkImage)
 
 static SkImage_Base* asIB(SkImage* image) {
     return static_cast<SkImage_Base*>(image);
 }
 
+static const SkImage_Base* asIB(const SkImage* image) {
+    return static_cast<const SkImage_Base*>(image);
+}
+
 uint32_t SkImage::NextUniqueID() {
     static int32_t gUniqueID;
 
     // never return 0;
     uint32_t id;
     do {
         id = sk_atomic_inc(&gUniqueID) + 1;
     } while (0 == id);
     return id;
 }
 
 void SkImage::draw(SkCanvas* canvas, SkScalar x, SkScalar y,
                    const SkPaint* paint) {
     asIB(this)->onDraw(canvas, x, y, paint);
 }
 
 GrTexture* SkImage::getTexture() {
     return asIB(this)->onGetTexture();
 }
+
+SkData* SkImage::encode(EncodeType et, int quality) const {
+    SkImageEncoder::Type iet = (et == kPNG_EncodeType)
+            ? SkImageEncoder::kPNG_Type : SkImageEncoder::kJPEG_Type;
+    SkBitmap rocopy;
+
+    if (asIB(this)->getROPixels(&rocopy)) {
+        SkAutoTDelete<SkImageEncoder> encoder(SkImageEncoder::Create(iet));
+        if (encoder.get()) {
+            return encoder->encodeData(rocopy, quality);
+        }
+    }
+    return NULL;
+}