change pixel-serializer to support reencoding existing data

include/core/SkImageEncoder.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageEncoder_DEFINED
 #define SkImageEncoder_DEFINED
 
 #include "SkImageInfo.h"
 #include "SkTRegistry.h"
 
 class SkBitmap;
 class SkData;
+class SkPixmap;
+class SkPixelSerializer;
 class SkWStream;
 
 class SkImageEncoder {
 public:
     // TODO (scroggo): Merge with SkEncodedFormat.
     enum Type {
         kUnknown_Type,
         kBMP_Type,
         kGIF_Type,
         kICO_Type,
@@ skipping 27 matching lines @@
      */
     bool encodeFile(const char file[], const SkBitmap& bm, int quality);
 
     /**
      * Encode bitmap 'bm' in the desired format, writing results to
      * stream 'stream', at quality level 'quality' (which can be in
      * range 0-100). Returns false on failure.
      */
     bool encodeStream(SkWStream* stream, const SkBitmap& bm, int quality);
 
+    SkPixelSerializer* refSerializer();
+
     static SkData* EncodeData(const SkImageInfo&, const void* pixels, size_t rowBytes,
                               Type, int quality);
+    static SkData* EncodeData(const SkPixmap&, Type, int quality);
     static SkData* EncodeData(const SkBitmap&, Type, int quality);
 
     static bool EncodeFile(const char file[], const SkBitmap&, Type,
                            int quality);
     static bool EncodeStream(SkWStream*, const SkBitmap&, Type,
                            int quality);
 
+    /**
+     *  If the existing data can be re-encoded into the specified type (efficiently), this
+     *  returns that new data (which the caller must unref()). If not, this returns null.
+     */
+    static SkData* ReencodeData(SkData* encoded, Type);
+
 protected:
     /**
      * Encode bitmap 'bm' in the desired format, writing results to
      * stream 'stream', at quality level 'quality' (which can be in
      * range 0-100).
      *
      * This must be overridden by each SkImageEncoder implementation.
      */
     virtual bool onEncode(SkWStream* stream, const SkBitmap& bm, int quality) = 0;
+
+    virtual SkData* onReencodeData(SkData*) { return nullptr; }
 };
 
 // This macro declares a global (i.e., non-class owned) creation entry point
 // for each encoder (e.g., CreateJPEGImageEncoder)
 #define DECLARE_ENCODER_CREATOR(codec)          \
     SkImageEncoder *Create ## codec ();
 
 // This macro defines the global creation entry point for each encoder. Each
 // encoder implementation that registers with the encoder factory must call it.
 #define DEFINE_ENCODER_CREATOR(codec) \
@@ skipping 12 matching lines @@
 DECLARE_ENCODER_CREATOR(WEBPImageEncoder);
 
 #ifdef SK_BUILD_FOR_IOS
 DECLARE_ENCODER_CREATOR(PNGImageEncoder_IOS);
 #endif
 
 // Typedef to make registering encoder callback easier
 // This has to be defined outside SkImageEncoder. :(
 typedef SkTRegistry<SkImageEncoder*(*)(SkImageEncoder::Type)> SkImageEncoder_EncodeReg;
 #endif