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      1 /*
      2  * Copyright 2015 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkCodec.h"
      9 #include "SkColorTable.h"
     10 #include "SkEncodedFormat.h"
     11 #include "SkImageInfo.h"
     12 #include "SkRefCnt.h"
     13 #include "SkSwizzler.h"
     14 
     15 #ifdef SKIA_PNG_PREFIXED
     16     // this must proceed png.h
     17     #include "pngprefix.h"
     18 #endif
     19 #include "png.h"
     20 
     21 class SkScanlineDecoder;
     22 class SkStream;
     23 
     24 class SkPngCodec : public SkCodec {
     25 public:
     26     // Assumes IsPng was called and returned true.
     27     static SkCodec* NewFromStream(SkStream*);
     28     static bool IsPng(SkStream*);
     29 protected:
     30     Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, SkPMColor*, int*)
     31             override;
     32     SkEncodedFormat onGetEncodedFormat() const override { return kPNG_SkEncodedFormat; }
     33     SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo, const Options& options,
     34                                             SkPMColor ctable[], int* ctableCount) override;
     35     bool onReallyHasAlpha() const override { return fReallyHasAlpha; }
     36 private:
     37     png_structp                 fPng_ptr;
     38     png_infop                   fInfo_ptr;
     39 
     40     // These are stored here so they can be used both by normal decoding and scanline decoding.
     41     SkAutoTUnref<SkColorTable>  fColorTable;    // May be unpremul.
     42     SkAutoTDelete<SkSwizzler>   fSwizzler;
     43 
     44     SkSwizzler::SrcConfig       fSrcConfig;
     45     int                         fNumberPasses;
     46     bool                        fReallyHasAlpha;
     47 
     48     SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop);
     49     ~SkPngCodec();
     50 
     51     // Helper to set up swizzler and color table. Also calls png_read_update_info.
     52     Result initializeSwizzler(const SkImageInfo& requestedInfo, void* dst,
     53                               size_t rowBytes, const Options&, SkPMColor*, int* ctableCount);
     54     // Calls rewindIfNeeded, and returns true if the decoder can continue.
     55     bool handleRewind();
     56     bool decodePalette(bool premultiply, int bitDepth, int* ctableCount);
     57     void finish();
     58     void destroyReadStruct();
     59 
     60     friend class SkPngScanlineDecoder;
     61 
     62     typedef SkCodec INHERITED;
     63 };
     64