Option for SkCodec to treat dst as all zeroes.

include/core/SkImageGenerator.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageGenerator_DEFINED
 #define SkImageGenerator_DEFINED
 
 #include "SkColor.h"
 #include "SkImageInfo.h"
 
 class SkBitmap;
 class SkData;
 class SkImageGenerator;
 
+//#define SK_SUPPORT_LEGACY_OPTIONLESS_GET_PIXELS
+
 /**
  *  Takes ownership of SkImageGenerator.  If this method fails for
  *  whatever reason, it will return false and immediatetely delete
  *  the generator.  If it succeeds, it will modify destination
  *  bitmap.
  *
  *  If generator is NULL, will safely return false.
  *
  *  If this fails or when the SkDiscardablePixelRef that is
  *  installed into destination is destroyed, it will call
@@ skipping 82 matching lines @@
          *  supported for this input.
          */
         kCouldNotRewind,
         /**
          *  This method is not implemented by this generator.
          */
         kUnimplemented,
     };
 
     /**
+     *  Whether or not the memory passed to getPixels is zero initialized.
+     */
+    enum ZeroInitialized {
+        /**
+         *  The memory passed to getPixels is zero initialized. The SkCodec
+         *  may take advantage of this by skipping writing zeroes.
+         */
+        kYes_ZeroInitialized,
+        /**
+         *  The memory passed to getPixels has not been initialized to zero,
+         *  so the SkCodec must write all zeroes to memory.
+         *
+         *  This is the default. It will be used if no Options struct is used.
+         */
+        kNo_ZeroInitialized,
+    };
+
+    /**
+     *  Additional options to pass to getPixels.
+     */
+    struct Options {
+        Options()
+            : fZeroInitialized(kNo_ZeroInitialized) {}
+
+        ZeroInitialized fZeroInitialized;
+    };
+
+    /**
      *  Decode into the given pixels, a block of memory of size at
      *  least (info.fHeight - 1) * rowBytes + (info.fWidth *
      *  bytesPerPixel)
      *
      *  Repeated calls to this function should give the same results,
      *  allowing the PixelRef to be immutable.
      *
      *  @param info A description of the format (config, size)
      *         expected by the caller.  This can simply be identical
      *         to the info returned by getInfo().
      *
      *         This contract also allows the caller to specify
      *         different output-configs, which the implementation can
      *         decide to support or not.
      *
      *         A size that does not match getInfo() implies a request
      *         to scale. If the generator cannot perform this scale,
      *         it will return kInvalidScale.
      *
      *  If info is kIndex8_SkColorType, then the caller must provide storage for up to 256
      *  SkPMColor values in ctable. On success the generator must copy N colors into that storage,
      *  (where N is the logical number of table entries) and set ctableCount to N.
      *
      *  If info is not kIndex8_SkColorType, then the last two parameters may be NULL. If ctableCount
      *  is not null, it will be set to 0.
      *
      *  @return Result kSuccess, or another value explaining the type of failure.
      */
-    Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+    Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, const Options*,
                      SkPMColor ctable[], int* ctableCount);
 
     /**
-     *  Simplified version of getPixels() that asserts that info is NOT kIndex8_SkColorType.
+     *  Simplified version of getPixels() that asserts that info is NOT kIndex8_SkColorType and
+     *  uses the default Options.
      */
     Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
 
     /**
      *  If planes or rowBytes is NULL or if any entry in planes is NULL or if any entry in rowBytes
      *  is 0, this imagegenerator should output the sizes and return true if it can efficiently
      *  return YUV planar data. If it cannot, it should return false. Note that either planes and
      *  rowBytes are both fully defined and non NULL/non 0 or they are both NULL or have NULL or 0
      *  entries only. Having only partial planes/rowBytes information is not supported.
      *
      *  If all planes and rowBytes entries are non NULL or non 0, then it should copy the
      *  associated YUV data into those planes of memory supplied by the caller. It should validate
      *  that the sizes match what it expected. If the sizes do not match, it should return false.
      */
     bool getYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                        SkYUVColorSpace* colorSpace);
 
     /**
      *  If the default image decoder system can interpret the specified (encoded) data, then
      *  this returns a new ImageGenerator for it. Otherwise this returns NULL. Either way
      *  the caller is still responsible for managing their ownership of the data.
      */
     static SkImageGenerator* NewFromData(SkData*);
 
 protected:
     virtual SkData* onRefEncodedData();
     virtual bool onGetInfo(SkImageInfo* info);
+#ifdef SK_SUPPORT_LEGACY_OPTIONLESS_GET_PIXELS
     virtual Result onGetPixels(const SkImageInfo& info,
                                void* pixels, size_t rowBytes,
                                SkPMColor ctable[], int* ctableCount);
+#endif
+    virtual Result onGetPixels(const SkImageInfo& info,
+                               void* pixels, size_t rowBytes, const Options&,
+                               SkPMColor ctable[], int* ctableCount);
     virtual bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3]);
     virtual bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                                  SkYUVColorSpace* colorSpace);
 };
 
 #endif  // SkImageGenerator_DEFINED