root/Source/platform/image-decoders/ImageDecoder.cpp

DEFINITIONS

1. copyFromSharedBuffer
2. matchesGIFSignature
3. matchesPNGSignature
4. matchesJPEGSignature
5. matchesWebPSignature
6. matchesBMPSignature
7. matchesICOSignature
8. matchesCURSignature
9. create
10. frameHasAlphaAtIndex
11. frameIsCompleteAtIndex
12. frameBytesAtIndex
13. clearCacheExceptFrame
14. clearFrameBuffer
15. findRequiredPreviousFrame

/*
 * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include "platform/image-decoders/ImageDecoder.h"

#include "platform/image-decoders/bmp/BMPImageDecoder.h"
#include "platform/image-decoders/gif/GIFImageDecoder.h"
#include "platform/image-decoders/ico/ICOImageDecoder.h"
#include "platform/image-decoders/jpeg/JPEGImageDecoder.h"
#include "platform/image-decoders/png/PNGImageDecoder.h"
#include "platform/image-decoders/webp/WEBPImageDecoder.h"
#include "wtf/PassOwnPtr.h"

namespace WebCore {

static unsigned copyFromSharedBuffer(char* buffer, unsigned bufferLength, const SharedBuffer& sharedBuffer, unsigned offset)
{
    unsigned bytesExtracted = 0;
    const char* moreData;
    while (unsigned moreDataLength = sharedBuffer.getSomeData(moreData, offset)) {
        unsigned bytesToCopy = std::min(bufferLength - bytesExtracted, moreDataLength);
        memcpy(buffer + bytesExtracted, moreData, bytesToCopy);
        bytesExtracted += bytesToCopy;
        if (bytesExtracted == bufferLength)
            break;
        offset += bytesToCopy;
    }
    return bytesExtracted;
}

inline bool matchesGIFSignature(char* contents)
{
    return !memcmp(contents, "GIF87a", 6) || !memcmp(contents, "GIF89a", 6);
}

inline bool matchesPNGSignature(char* contents)
{
    return !memcmp(contents, "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A", 8);
}

inline bool matchesJPEGSignature(char* contents)
{
    return !memcmp(contents, "\xFF\xD8\xFF", 3);
}

inline bool matchesWebPSignature(char* contents)
{
    return !memcmp(contents, "RIFF", 4) && !memcmp(contents + 8, "WEBPVP", 6);
}

inline bool matchesBMPSignature(char* contents)
{
    return !memcmp(contents, "BM", 2);
}

inline bool matchesICOSignature(char* contents)
{
    return !memcmp(contents, "\x00\x00\x01\x00", 4);
}

inline bool matchesCURSignature(char* contents)
{
    return !memcmp(contents, "\x00\x00\x02\x00", 4);
}

PassOwnPtr<ImageDecoder> ImageDecoder::create(const SharedBuffer& data, ImageSource::AlphaOption alphaOption, ImageSource::GammaAndColorProfileOption gammaAndColorProfileOption)
{
    static const unsigned longestSignatureLength = sizeof("RIFF????WEBPVP") - 1;
    ASSERT(longestSignatureLength == 14);

    size_t maxDecodedBytes = blink::Platform::current()->maxDecodedImageBytes();

    char contents[longestSignatureLength];
    if (copyFromSharedBuffer(contents, longestSignatureLength, data, 0) < longestSignatureLength)
        return nullptr;

    if (matchesJPEGSignature(contents))
        return adoptPtr(new JPEGImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    if (matchesPNGSignature(contents))
        return adoptPtr(new PNGImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    if (matchesGIFSignature(contents))
        return adoptPtr(new GIFImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    if (matchesICOSignature(contents) || matchesCURSignature(contents))
        return adoptPtr(new ICOImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    if (matchesWebPSignature(contents))
        return adoptPtr(new WEBPImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    if (matchesBMPSignature(contents))
        return adoptPtr(new BMPImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes));

    return nullptr;
}

bool ImageDecoder::frameHasAlphaAtIndex(size_t index) const
{
    return !frameIsCompleteAtIndex(index) || m_frameBufferCache[index].hasAlpha();
}

bool ImageDecoder::frameIsCompleteAtIndex(size_t index) const
{
    return (index < m_frameBufferCache.size()) &&
        (m_frameBufferCache[index].status() == ImageFrame::FrameComplete);
}

unsigned ImageDecoder::frameBytesAtIndex(size_t index) const
{
    if (m_frameBufferCache.size() <= index || m_frameBufferCache[index].status() == ImageFrame::FrameEmpty)
        return 0;
    // FIXME: Use the dimension of the requested frame.
    return m_size.area() * sizeof(ImageFrame::PixelData);
}

size_t ImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
{
    // Don't clear if there are no frames or only one frame.
    if (m_frameBufferCache.size() <= 1)
        return 0;

    size_t frameBytesCleared = 0;
    for (size_t i = 0; i < m_frameBufferCache.size(); ++i) {
        if (i != clearExceptFrame) {
            frameBytesCleared += frameBytesAtIndex(i);
            clearFrameBuffer(i);
        }
    }
    return frameBytesCleared;
}

void ImageDecoder::clearFrameBuffer(size_t frameIndex)
{
    m_frameBufferCache[frameIndex].clearPixelData();
}

size_t ImageDecoder::findRequiredPreviousFrame(size_t frameIndex, bool frameRectIsOpaque)
{
    ASSERT(frameIndex <= m_frameBufferCache.size());
    if (!frameIndex) {
        // The first frame doesn't rely on any previous data.
        return kNotFound;
    }

    const ImageFrame* currBuffer = &m_frameBufferCache[frameIndex];
    if ((frameRectIsOpaque || currBuffer->alphaBlendSource() == ImageFrame::BlendAtopBgcolor)
        && currBuffer->originalFrameRect().contains(IntRect(IntPoint(), size())))
        return kNotFound;

    // The starting state for this frame depends on the previous frame's
    // disposal method.
    size_t prevFrame = frameIndex - 1;
    const ImageFrame* prevBuffer = &m_frameBufferCache[prevFrame];
    ASSERT(prevBuffer->requiredPreviousFrameIndexValid());

    switch (prevBuffer->disposalMethod()) {
    case ImageFrame::DisposeNotSpecified:
    case ImageFrame::DisposeKeep:
        // prevFrame will be used as the starting state for this frame.
        // FIXME: Be even smarter by checking the frame sizes and/or alpha-containing regions.
        return prevFrame;
    case ImageFrame::DisposeOverwritePrevious:
        // Frames that use the DisposeOverwritePrevious method are effectively
        // no-ops in terms of changing the starting state of a frame compared to
        // the starting state of the previous frame, so skip over them and
        // return the required previous frame of it.
        return prevBuffer->requiredPreviousFrameIndex();
    case ImageFrame::DisposeOverwriteBgcolor:
        // If the previous frame fills the whole image, then the current frame
        // can be decoded alone. Likewise, if the previous frame could be
        // decoded without reference to any prior frame, the starting state for
        // this frame is a blank frame, so it can again be decoded alone.
        // Otherwise, the previous frame contributes to this frame.
        return (prevBuffer->originalFrameRect().contains(IntRect(IntPoint(), size()))
            || (prevBuffer->requiredPreviousFrameIndex() == kNotFound)) ? kNotFound : prevFrame;
    default:
        ASSERT_NOT_REACHED();
        return kNotFound;
    }
}

} // namespace WebCore