WIP: Implement APNG

third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h

Index: third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h
index 4144201a9b66088d12704bdf2d64feb9eac6c822..bbdeb13dda2b9e565c3d3828c072e8ce4a96b158 100644
--- a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h
+++ b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageReader.h
@@ -29,6 +29,10 @@
 #include "platform/image-decoders/png/PNGImageDecoder.h"
 #include "png.h"
 
+namespace blink {
+
+class SegmentReader;
+
 #if !defined(PNG_LIBPNG_VER_MAJOR) || !defined(PNG_LIBPNG_VER_MINOR)
 #error version error: compile against a versioned libpng.
 #endif
@@ -40,45 +44,119 @@
 #define JMPBUF(png_ptr) png_ptr->jmpbuf
 #endif
 
-namespace blink {
-
-class SegmentReader;
-
 class PLATFORM_EXPORT PNGImageReader final {
   USING_FAST_MALLOC(PNGImageReader);
   WTF_MAKE_NONCOPYABLE(PNGImageReader);
 
  public:
-  PNGImageReader(PNGImageDecoder*, size_t offset);
+  PNGImageReader(PNGImageDecoder*, size_t initialOffset);
   ~PNGImageReader();
 
-  bool decode(const SegmentReader&, bool sizeOnly);
+  struct FrameInfo {
+    // The offset where the frame data of this frame starts.
+    size_t startOffset;
+    // The number of bytes that contain frame data, starting at startOffset.
+    size_t byteLength;
+    size_t duration;
+    IntRect frameRect;
+    uint8_t disposalMethod;
+    uint8_t alphaBlend;
+  };
+
+  // This method tries to parse the data stream in the SegmentReader, up to
+  // the point where the PNGParseQuery can be answered.
+  // @return true when the query is fulfilled.
+  //         false when:
+  //          A) not enough data provided
+  //          B) the data processing by libpng fails. In this case, it also
+  //             calls setFailed() on m_decoder.
+  bool parse(SegmentReader&, PNGImageDecoder::PNGParseQuery);
+
+  void decode(SegmentReader&, size_t);
+  const FrameInfo& frameInfo(size_t) const;
+
+  // This will return the number of frames that have been detected in the
+  // stream so far. If an incomplete stream is provided, this number is not
+  // final. However, all frame info for the frames up to this number is
+  // available so it can be used by the client if it wants to.
+  size_t frameCount() const;
+
+  // This is called by the the libpng callback that handles unknown chunks.
+  void parseAnimationChunk(const char* tag,
+                           const void* dataChunk,
+                           size_t length);
+
+  // |m_parseCompleted| becomes true when
+  //  a) the png is determined to be non-animated, if no acTL chunk is found
+  //     before the IDAT chunk, or
+  //  b) when the IEND chunk is seen for animated pngs.
+  bool parseCompleted() const { return m_parseCompleted; };
+  void setParseCompleted(bool completed) { m_parseCompleted = completed; };

[scroggo_chromium, 2016/12/08 13:59:09]

nit: this is only called with true, and I think it would be weird to call it
with false. Maybe change it to

setParseCompleted() { m_parseCompleted = true; }

[joostouwerling, 2016/12/08 16:28:39]

Done.

+
+  // This method indicates for *animated* PNGs whether the first frame is fully
+  // received. That is, when the fcTL chunk of the next frame has been received.
+  bool firstFrameFullyReceived() const;
+
+  // This method is called when a frame with status ImageFrame::FramePartial
+  // gets cleared in PNGImageDecoder.
+  //
+  // For |frameIndex| > 0, no action is necessary, since each decode call will
+  // decode the frame completely from start to end.
+  //
+  // For |frameIndex| == 0, |m_progressiveDecodeOffset| will be set to 0, to
+  // make sure progressive decoding is started from the beginning of the frame.
+  void clearDecodeState(size_t frameIndex);
+
   png_structp pngPtr() const { return m_png; }
   png_infop infoPtr() const { return m_info; }
 
-  size_t getReadOffset() const { return m_readOffset; }
-  void setReadOffset(size_t offset) { m_readOffset = offset; }
-  size_t currentBufferSize() const { return m_currentBufferSize; }
-  bool decodingSizeOnly() const { return m_decodingSizeOnly; }
-  void setHasAlpha(bool hasAlpha) { m_hasAlpha = hasAlpha; }
-  bool hasAlpha() const { return m_hasAlpha; }
-
   png_bytep interlaceBuffer() const { return m_interlaceBuffer.get(); }
   void createInterlaceBuffer(int size) {
     m_interlaceBuffer = wrapArrayUnique(new png_byte[size]);
   }
+  void clearInterlaceBuffer() { m_interlaceBuffer.reset(); }
 
  private:
   png_structp m_png;
   png_infop m_info;
   PNGImageDecoder* m_decoder;
+  // This indicates at what offset in the stream the PNG image starts.
+  const size_t m_initialOffset;
+  // This is used to keep track of how many bytes we've read during parsing.
   size_t m_readOffset;
-  size_t m_currentBufferSize;
-  bool m_decodingSizeOnly;
-  bool m_hasAlpha;
+
+  // This variable is used to do progressive decoding for the first frame. It
+  // keeps track of how many bytes have been processed so far.
+  size_t m_progressiveDecodeOffset;
+  // The offset where IDAT starts. This is used to re-use the complete set of
+  // info/header chunks when mimicking a png image for a frame.
+  size_t m_idatOffset;
+  // This flag is set to true when an fcTL chunk is encountered before the
+  // IDAT chunk(s). In that case, the IDAT data is the first frame. Otherwise,
+  // the IDAT is ignored for an animated image.
+  bool m_idatIsPartOfAnimation;
+  bool m_isAnimated;
+  bool m_parsedSignature;
+  bool m_parseCompleted;
+
   std::unique_ptr<png_byte[]> m_interlaceBuffer;
-};
 
-}  // namespace blink
+  Vector<FrameInfo, 1> m_frameInfo;
+  // This is used to temporarily store frame information, until it is pushed to
+  // |m_frameInfo|, when all frame data has been seen in the stream.
+  FrameInfo m_newFrame;
+
+  size_t processData(SegmentReader&, size_t offset, size_t length);
+  bool parseSize(SegmentReader&);
+  void parseFrameInfo(const png_byte* data);
+  void resetPNGStruct();
+  void startFrameDecoding(SegmentReader&, size_t);
+  // @return true if the complete frame has been decoded
+  //         false  otherwise
+  bool progressivelyDecodeFirstFrame(SegmentReader&);
+  void decodeFrame(SegmentReader&, size_t);
+  void endFrameDecoding();
+};
+};
 
 #endif