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

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 1169459df638d79d9a4262216f531274b139f402..3050e3b69d41d306326b2884e05d082e9e6d8882 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -9,6 +9,7 @@
 #include "SkImagePriv.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
+#include "../images/SkImageEncoder.h"
 
 SK_DEFINE_INST_COUNT(SkImage)
 
@@ -16,6 +17,10 @@ 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;
 
@@ -35,3 +40,17 @@ void SkImage::draw(SkCanvas* canvas, SkScalar x, SkScalar y,
 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;
+}