GIFImageDecoder.h   [plain text]

/*
 * Copyright (C) 2006 Apple Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef GIFImageDecoder_h
#define GIFImageDecoder_h

#include "ImageDecoder.h"

class GIFImageReader;

namespace WebCore {

    // This class decodes the GIF image format.
    class GIFImageDecoder final : public ImageDecoder {
    public:
        GIFImageDecoder(ImageSource::AlphaOption, ImageSource::GammaAndColorProfileOption);
        virtual ~GIFImageDecoder();

        enum GIFQuery { GIFFullQuery, GIFSizeQuery, GIFFrameCountQuery };

        // ImageDecoder
        String filenameExtension() const override { return "gif"; }
        void setData(SharedBuffer& data, bool allDataReceived) override;
        bool isSizeAvailable() override;
        bool setSize(unsigned width, unsigned height) override;
        size_t frameCount() override;
        int repetitionCount() const override;
        ImageFrame* frameBufferAtIndex(size_t index) override;
        // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
        // accessing deleted memory, especially when calling this from inside
        // GIFImageReader!
        bool setFailed() override;
        void clearFrameBufferCache(size_t clearBeforeFrame) override;

        // Callbacks from the GIF reader.
        bool haveDecodedRow(unsigned frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
        bool frameComplete(unsigned frameIndex, unsigned frameDuration, ImageFrame::FrameDisposalMethod disposalMethod);
        void gifComplete();

    private:
        // If the query is GIFFullQuery, decodes the image up to (but not
        // including) |haltAtFrame|.  Otherwise, decodes as much as is needed to
        // answer the query, ignoring bitmap data.  If decoding fails but there
        // is no more data coming, sets the "decode failure" flag.
        void decode(unsigned haltAtFrame, GIFQuery);

        // Called to initialize the frame buffer with the given index, based on
        // the previous frame's disposal method. Returns true on success. On
        // failure, this will mark the image as failed.
        bool initFrameBuffer(unsigned frameIndex);

        bool m_currentBufferSawAlpha;
        mutable int m_repetitionCount;
        std::unique_ptr<GIFImageReader> m_reader;
    };

} // namespace WebCore

#endif