add setPreserveSrcDepth to replace PrefTable API for android

include/core/SkImageDecoder.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageDecoder_DEFINED
 #define SkImageDecoder_DEFINED
 
@@ skipping 187 matching lines @@
     void setPrefConfigTable(const PrefConfigTable&);
 
     /**
      *  Do not use a PrefConfigTable to determine the output config. This
      *  is the default, so there is no need to call unless a PrefConfigTable
      *  was previously set.
      */
     void resetPrefConfigTable() { fUsePrefTable = false; }
 #endif
 
+    /**
+     *  By default, the codec will try to comply with the "pref" colortype
+     *  that is passed to decode() or decodeSubset(). However, this can be called
+     *  to override that, causing the codec to try to match the src depth instead
+     *  (as shown below).
+     *
+     *      src_8Index  -> kIndex_8_SkColorType
+     *      src_8Gray   -> kN32_SkColorType
+     *      src_8bpc    -> kN32_SkColorType
+     */
+    void setPreserveSrcDepth(bool preserve) {
+        fPreserveSrcDepth = preserve;
+    }
+
     SkBitmap::Allocator* getAllocator() const { return fAllocator; }
     SkBitmap::Allocator* setAllocator(SkBitmap::Allocator*);
 
     // sample-size, if set to > 1, tells the decoder to return a smaller than
     // original bitmap, sampling 1 pixel for every size pixels. e.g. if sample
     // size is set to 3, then the returned bitmap will be 1/3 as wide and high,
     // and will contain 1/9 as many pixels as the original.
     // Note: this is a hint, and the codec may choose to ignore this, or only
     // approximate the sample size.
     int getSampleSize() const { return fSampleSize; }
@@ skipping 231 matching lines @@
 #ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
     Chooser*                fChooser;
 #endif
     SkBitmap::Allocator*    fAllocator;
     int                     fSampleSize;
     SkColorType             fDefaultPref;   // use if fUsePrefTable is false
 #ifdef SK_SUPPORT_LEGACY_BITMAP_CONFIG
     PrefConfigTable         fPrefTable;     // use if fUsePrefTable is true
     bool                    fUsePrefTable;
 #endif
+    bool                    fPreserveSrcDepth;
     bool                    fDitherImage;
     bool                    fSkipWritingZeroes;
     mutable bool            fShouldCancelDecode;
     bool                    fPreferQualityOverSpeed;
     bool                    fRequireUnpremultipliedColors;
 };
 
 /** Calling newDecoder with a stream returns a new matching imagedecoder
     instance, or NULL if none can be found. The caller must manage its ownership
     of the stream as usual, calling unref() when it is done, as the returned
@@ skipping 41 matching lines @@
 DECLARE_DECODER_CREATOR(WEBPImageDecoder);
 DECLARE_DECODER_CREATOR(PKMImageDecoder);
 DECLARE_DECODER_CREATOR(KTXImageDecoder);
 
 // Typedefs to make registering decoder and formatter callbacks easier.
 // These have to be defined outside SkImageDecoder. :(
 typedef SkTRegistry<SkImageDecoder*(*)(SkStreamRewindable*)>        SkImageDecoder_DecodeReg;
 typedef SkTRegistry<SkImageDecoder::Format(*)(SkStreamRewindable*)> SkImageDecoder_FormatReg;
 
 #endif