text: /*
   * Copyright (C) 2006 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #ifndef SkImageDecoder_DEFINED
  #define SkImageDecoder_DEFINED
  
  #include "SkBitmap.h"
  #include "SkRefCnt.h"
  
  class SkStream;
  
  /** \class SkImageDecoder
  
      Base class for decoding compressed images into a SkBitmap
  */
  class SK_API SkImageDecoder {
  public:
      virtual ~SkImageDecoder();
  
      enum Format {
          kUnknown_Format,
          kBMP_Format,
          kGIF_Format,
          kICO_Format,
          kJPEG_Format,
          kPNG_Format,
          kWBMP_Format,
  
          kLastKnownFormat = kWBMP_Format
      };
  
      /** Return the compressed data's format (see Format enum)
      */
      virtual Format getFormat() const;
  
      /** Returns true if the decoder should try to dither the resulting image.
          The default setting is true.
      */
      bool getDitherImage() const { return fDitherImage; }
  
      /** Set to true if the the decoder should try to dither the resulting image.
          The default setting is true.
      */
      void setDitherImage(bool dither) { fDitherImage = dither; }
  
      /** \class Peeker
  
          Base class for optional callbacks to retrieve meta/chunk data out of
          an image as it is being decoded.
      */
      class Peeker : public SkRefCnt {
      public:
          /** Return true to continue decoding, or false to indicate an error, which
              will cause the decoder to not return the image.
          */
          virtual bool peek(const char tag[], const void* data, size_t length) = 0;
      };
  
      Peeker* getPeeker() const { return fPeeker; }
      Peeker* setPeeker(Peeker*);
  
      /** \class Peeker
  
          Base class for optional callbacks to retrieve meta/chunk data out of
          an image as it is being decoded.
      */
      class Chooser : public SkRefCnt {
      public:
          virtual void begin(int count) {}
          virtual void inspect(int index, SkBitmap::Config config, int width, int height) {}
          /** Return the index of the subimage you want, or -1 to choose none of them.
          */
          virtual int choose() = 0;
      };
  
      Chooser* getChooser() const { return fChooser; }
      Chooser* setChooser(Chooser*);
  
      /** This optional table describes the caller's preferred config based on
          information about the src data. For this table, the src attributes are
          described in terms of depth (index (8), 16, 32/24) and if there is
          per-pixel alpha. These inputs combine to create an index into the
          pref[] table, which contains the caller's preferred config for that
          input, or kNo_Config if there is no preference.
  
          To specify no preferrence, call setPrefConfigTable(NULL), which is
          the default.
  
          Note, it is still at the discretion of the codec as to what output
          config is actually returned, as it may not be able to support the
          caller's preference.
  
          Here is how the index into the table is computed from the src:
              depth [8, 16, 32/24] -> 0, 2, 4
              alpha [no, yes] -> 0, 1
          The two index values are OR'd together.
              src: 8-index, no-alpha  -> 0
              src: 8-index, yes-alpha -> 1
              src: 16bit,   no-alpha  -> 2    // e.g. 565
              src: 16bit,   yes-alpha -> 3    // e.g. 1555
              src: 32/24,   no-alpha  -> 4
              src: 32/24,   yes-alpha -> 5
       */
      void setPrefConfigTable(const SkBitmap::Config pref[6]);
  
      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; }
      void setSampleSize(int size);
  
      /** Reset the sampleSize to its default of 1
       */
      void resetSampleSize() { this->setSampleSize(1); }
  
      /** Decoding is synchronous, but for long decodes, a different thread can
          call this method safely. This sets a state that the decoders will
          periodically check, and if they see it changed to cancel, they will
          cancel. This will result in decode() returning false. However, there is
          no guarantee that the decoder will see the state change in time, so
          it is possible that cancelDecode() will be called, but will be ignored
          and decode() will return true (assuming no other problems were
          encountered).
  
          This state is automatically reset at the beginning of decode().
       */
      void cancelDecode() {
          // now the subclass must query shouldCancelDecode() to be informed
          // of the request
          fShouldCancelDecode = true;
      }
  
      /** Passed to the decode method. If kDecodeBounds_Mode is passed, then
          only the bitmap's width/height/config need be set. If kDecodePixels_Mode
          is passed, then the bitmap must have pixels or a pixelRef.
      */
      enum Mode {
          kDecodeBounds_Mode, //!< only return width/height/config in bitmap
          kDecodePixels_Mode  //!< return entire bitmap (including pixels)
      };
  
      /** Given a stream, decode it into the specified bitmap.
          If the decoder can decompress the image, it calls bitmap.setConfig(),
          and then if the Mode is kDecodePixels_Mode, call allocPixelRef(),
          which will allocated a pixelRef. To access the pixel memory, the codec
          needs to call lockPixels/unlockPixels on the
          bitmap. It can then set the pixels with the decompressed image.
      *   If the image cannot be decompressed, return false. After the
      *   decoding, the function converts the decoded config in bitmap
      *   to pref if possible. Whether a conversion is feasible is
      *   tested by Bitmap::canCopyTo(pref).
  
          note: document use of Allocator, Peeker and Chooser
      */
      bool decode(SkStream*, SkBitmap* bitmap, SkBitmap::Config pref, Mode);
      bool decode(SkStream* stream, SkBitmap* bitmap, Mode mode) {
          return this->decode(stream, bitmap, SkBitmap::kNo_Config, mode);
      }
  
      /** Given a stream, this will try to find an appropriate decoder object.
          If none is found, the method returns NULL.
      */
      static SkImageDecoder* Factory(SkStream*);
  
      /** Decode the image stored in the specified file, and store the result
          in bitmap. Return true for success or false on failure.
  
          If pref is kNo_Config, then the decoder is free to choose the most natural
          config given the image data. If pref something other than kNo_Config,
          the decoder will attempt to decode the image into that format, unless
          there is a conflict (e.g. the image has per-pixel alpha and the bitmap's
          config does not support that), in which case the decoder will choose a
          closest match configuration.
  
          @param format On success, if format is non-null, it is set to the format
                        of the decoded file. On failure it is ignored.
      */
      static bool DecodeFile(const char file[], SkBitmap* bitmap,
                             SkBitmap::Config prefConfig, Mode,
                             Format* format = NULL);
      static bool DecodeFile(const char file[], SkBitmap* bitmap) {
          return DecodeFile(file, bitmap, SkBitmap::kNo_Config,
                            kDecodePixels_Mode, NULL);
      }
      /** Decode the image stored in the specified memory buffer, and store the
          result in bitmap. Return true for success or false on failure.
  
          If pref is kNo_Config, then the decoder is free to choose the most natural
          config given the image data. If pref something other than kNo_Config,
          the decoder will attempt to decode the image into that format, unless
          there is a conflict (e.g. the image has per-pixel alpha and the bitmap's
          config does not support that), in which case the decoder will choose a
          closest match configuration.
  
          @param format On success, if format is non-null, it is set to the format
                         of the decoded buffer. On failure it is ignored.
       */
      static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap,
                               SkBitmap::Config prefConfig, Mode,
                               Format* format = NULL);
      static bool DecodeMemory(const void* buffer, size_t size, SkBitmap* bitmap){
          return DecodeMemory(buffer, size, bitmap, SkBitmap::kNo_Config,
                              kDecodePixels_Mode, NULL);
      }
      /** Decode the image stored in the specified SkStream, and store the result
          in bitmap. Return true for success or false on failure.
  
          If pref is kNo_Config, then the decoder is free to choose the most
          natural config given the image data. If pref something other than
          kNo_Config, the decoder will attempt to decode the image into that
          format, unless there is a conflict (e.g. the image has per-pixel alpha
          and the bitmap's config does not support that), in which case the
          decoder will choose a closest match configuration.
  
          @param format On success, if format is non-null, it is set to the format
                        of the decoded stream. On failure it is ignored.
       */
      static bool DecodeStream(SkStream* stream, SkBitmap* bitmap,
                               SkBitmap::Config prefConfig, Mode,
                               Format* format = NULL);
      static bool DecodeStream(SkStream* stream, SkBitmap* bitmap) {
          return DecodeStream(stream, bitmap, SkBitmap::kNo_Config,
                              kDecodePixels_Mode, NULL);
      }
  
      /** Return the default config for the running device.
          Currently this used as a suggestion to image decoders that need to guess
          what config they should decode into.
          Default is kNo_Config, but this can be changed with SetDeviceConfig()
      */
      static SkBitmap::Config GetDeviceConfig();
      /** Set the default config for the running device.
          Currently this used as a suggestion to image decoders that need to guess
          what config they should decode into.
          Default is kNo_Config.
          This can be queried with GetDeviceConfig()
      */
      static void SetDeviceConfig(SkBitmap::Config);
  
    /** @cond UNIT_TEST */
      SkDEBUGCODE(static void UnitTest();)
    /** @endcond */
  
  protected:
      // must be overridden in subclasses. This guy is called by decode(...)
      virtual bool onDecode(SkStream*, SkBitmap* bitmap, Mode) = 0;
  
      /** Can be queried from within onDecode, to see if the user (possibly in
          a different thread) has requested the decode to cancel. If this returns
          true, your onDecode() should stop and return false.
          Each subclass needs to decide how often it can query this, to balance
          responsiveness with performance.
  
          Calling this outside of onDecode() may return undefined values.
       */
  
  public:
      bool shouldCancelDecode() const { return fShouldCancelDecode; }
  
  protected:
      SkImageDecoder();
  
      // helper function for decoders to handle the (common) case where there is only
      // once choice available in the image file.
      bool chooseFromOneChoice(SkBitmap::Config config, int width, int height) const;
  
      /*  Helper for subclasses. Call this to allocate the pixel memory given the bitmap's
          width/height/rowbytes/config. Returns true on success. This method handles checking
          for an optional Allocator.
      */
      bool allocPixelRef(SkBitmap*, SkColorTable*) const;
  
      enum SrcDepth {
          kIndex_SrcDepth,
          k16Bit_SrcDepth,
          k32Bit_SrcDepth
      };
      /** The subclass, inside onDecode(), calls this to determine the config of
          the returned bitmap. SrcDepth and hasAlpha reflect the raw data of the
          src image. This routine returns the caller's preference given
          srcDepth and hasAlpha, or kNo_Config if there is no preference.
  
          Note: this also takes into account GetDeviceConfig(), so the subclass
          need not call that.
       */
      SkBitmap::Config getPrefConfig(SrcDepth, bool hasAlpha) const;
  
  private:
      Peeker*                 fPeeker;
      Chooser*                fChooser;
      SkBitmap::Allocator*    fAllocator;
      int                     fSampleSize;
      SkBitmap::Config        fDefaultPref;   // use if fUsePrefTable is false
      SkBitmap::Config        fPrefTable[6];  // use if fUsePrefTable is true
      bool                    fDitherImage;
      bool                    fUsePrefTable;
      mutable bool            fShouldCancelDecode;
  
      // illegal
      SkImageDecoder(const SkImageDecoder&);
      SkImageDecoder& operator=(const SkImageDecoder&);
  };
  
  /** 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
      decoder may have called ref() (and if so, the decoder is responsible for
      balancing its ownership when it is destroyed).
   */
  class SkImageDecoderFactory : public SkRefCnt {
  public:
      virtual SkImageDecoder* newDecoder(SkStream*) = 0;
  };
  
  class SkDefaultImageDecoderFactory : SkImageDecoderFactory {
  public:
      // calls SkImageDecoder::Factory(stream)
      virtual SkImageDecoder* newDecoder(SkStream* stream) {
          return SkImageDecoder::Factory(stream);
      }
  };
  
  
  #endif
  