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/*
* Copyright (C) 2006 Apple Computer, 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 COMPUTER, 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 COMPUTER, 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.
*/
#include "config.h"
#include "GIFImageDecoder.h"
#include "GIFImageReader.h"
namespace WebCore {
GIFImageDecoder::GIFImageDecoder()
: m_alreadyScannedThisDataForFrameCount(true)
, m_repetitionCount(cAnimationLoopOnce)
, m_readOffset(0)
{
}
GIFImageDecoder::~GIFImageDecoder()
{
}
void GIFImageDecoder::setData(SharedBuffer* data, bool allDataReceived)
{
if (m_failed)
return;
ImageDecoder::setData(data, allDataReceived);
// We need to rescan the frame count, as the new data may have changed it.
m_alreadyScannedThisDataForFrameCount = false;
if (!m_reader && !m_failed)
m_reader.set(new GIFImageReader(this));
}
bool GIFImageDecoder::isSizeAvailable()
{
if (!ImageDecoder::isSizeAvailable() && !failed() && m_reader)
decode(0, GIFSizeQuery);
return ImageDecoder::isSizeAvailable();
}
size_t GIFImageDecoder::frameCount()
{
if (!m_alreadyScannedThisDataForFrameCount) {
// FIXME: Scanning all the data has O(n^2) behavior if the data were to
// come in really slowly. Might be interesting to try to clone our
// existing read session to preserve state, but for now we just crawl
// all the data. Note that this is no worse than what ImageIO does on
// Mac right now (it also crawls all the data again).
GIFImageReader reader(0);
reader.read((const unsigned char*)m_data->data(), m_data->size(), GIFFrameCountQuery, static_cast<unsigned>(-1));
m_alreadyScannedThisDataForFrameCount = true;
m_frameBufferCache.resize(reader.images_count);
}
return m_frameBufferCache.size();
}
int GIFImageDecoder::repetitionCount() const
{
// This value can arrive at any point in the image data stream. Most GIFs
// in the wild declare it near the beginning of the file, so it usually is
// set by the time we've decoded the size, but (depending on the GIF and the
// packets sent back by the webserver) not always. Our caller is
// responsible for waiting until image decoding has finished to ask this if
// it needs an authoritative answer. In the meantime, we should default to
// "loop once".
if (m_reader) {
// Added wrinkle: ImageSource::clear() may destroy the reader, making
// the result from the reader _less_ authoritative on future calls. To
// detect this, the reader returns cLoopCountNotSeen (-2) instead of
// cAnimationLoopOnce (-1) when its current incarnation hasn't actually
// seen a loop count yet; in this case we return our previously-cached
// value.
const int repetitionCount = m_reader->loop_count;
if (repetitionCount != cLoopCountNotSeen)
m_repetitionCount = repetitionCount;
}
return m_repetitionCount;
}
RGBA32Buffer* GIFImageDecoder::frameBufferAtIndex(size_t index)
{
if (index >= frameCount())
return 0;
RGBA32Buffer& frame = m_frameBufferCache[index];
if (frame.status() != RGBA32Buffer::FrameComplete && m_reader)
decode(index + 1, GIFFullQuery); // Decode this frame.
return &frame;
}
void GIFImageDecoder::clearFrameBufferCache(size_t clearBeforeFrame)
{
// In some cases, like if the decoder was destroyed while animating, we
// can be asked to clear more frames than we currently have.
if (m_frameBufferCache.isEmpty())
return; // Nothing to do.
// The "-1" here is tricky. It does not mean that |clearBeforeFrame| is the
// last frame we wish to preserve, but rather that we never want to clear
// the very last frame in the cache: it's empty (so clearing it is
// pointless), it's partial (so we don't want to clear it anyway), or the
// cache could be enlarged with a future setData() call and it could be
// needed to construct the next frame (see comments below). Callers can
// always use ImageSource::clear(true, ...) to completely free the memory in
// this case.
clearBeforeFrame = std::min(clearBeforeFrame, m_frameBufferCache.size() - 1);
const Vector<RGBA32Buffer>::iterator end(m_frameBufferCache.begin() + clearBeforeFrame);
// We need to preserve frames such that:
// * We don't clear |end|
// * We don't clear the frame we're currently decoding
// * We don't clear any frame from which a future initFrameBuffer() call
// will copy bitmap data
// All other frames can be cleared. Because of the constraints on when
// ImageSource::clear() can be called (see ImageSource.h), we're guaranteed
// not to have non-empty frames after the frame we're currently decoding.
// So, scan backwards from |end| as follows:
// * If the frame is empty, we're still past any frames we care about.
// * If the frame is complete, but is DisposeOverwritePrevious, we'll
// skip over it in future initFrameBuffer() calls. We can clear it
// unless it's |end|, and keep scanning. For any other disposal method,
// stop scanning, as we've found the frame initFrameBuffer() will need
// next.
// * If the frame is partial, we're decoding it, so don't clear it; if it
// has a disposal method other than DisposeOverwritePrevious, stop
// scanning, as we'll only need this frame when decoding the next one.
Vector<RGBA32Buffer>::iterator i(end);
for (; (i != m_frameBufferCache.begin()) && ((i->status() == RGBA32Buffer::FrameEmpty) || (i->disposalMethod() == RGBA32Buffer::DisposeOverwritePrevious)); --i) {
if ((i->status() == RGBA32Buffer::FrameComplete) && (i != end))
i->clear();
}
// Now |i| holds the last frame we need to preserve; clear prior frames.
for (Vector<RGBA32Buffer>::iterator j(m_frameBufferCache.begin()); j != i; ++j) {
ASSERT(j->status() != RGBA32Buffer::FramePartial);
if (j->status() != RGBA32Buffer::FrameEmpty)
j->clear();
}
}
bool GIFImageDecoder::sizeNowAvailable(unsigned width, unsigned height)
{
if (!setSize(width, height))
return false;
prepareScaleDataIfNecessary();
return true;
}
void GIFImageDecoder::decodingHalted(unsigned bytesLeft)
{
m_readOffset = m_data->size() - bytesLeft;
}
bool GIFImageDecoder::haveDecodedRow(unsigned frameIndex, unsigned char* rowBuffer, unsigned char* rowEnd, unsigned rowNumber, unsigned repeatCount, bool writeTransparentPixels)
{
const GIFFrameReader* frameReader = m_reader->frame_reader;
// The pixel data and coordinates supplied to us are relative to the frame's
// origin within the entire image size, i.e.
// (frameReader->x_offset, frameReader->y_offset). There is no guarantee
// that (rowEnd - rowBuffer) == (size().width() - frameReader->x_offset), so
// we must ensure we don't run off the end of either the source data or the
// row's X-coordinates.
int xBegin = upperBoundScaledX(frameReader->x_offset);
int yBegin = upperBoundScaledY(frameReader->y_offset + rowNumber);
int xEnd = lowerBoundScaledX(std::min(xBegin + static_cast<int>(rowEnd - rowBuffer), size().width()) - 1, xBegin + 1) + 1;
int yEnd = lowerBoundScaledY(std::min(yBegin + static_cast<int>(repeatCount), size().height()) - 1, yBegin + 1) + 1;
if (!rowBuffer || (xBegin < 0) || (yBegin < 0) || (xEnd <= xBegin) || (yEnd <= yBegin))
return true;
// Get the colormap.
const unsigned char* colorMap;
unsigned colorMapSize;
if (frameReader->is_local_colormap_defined) {
colorMap = frameReader->local_colormap;
colorMapSize = (unsigned)frameReader->local_colormap_size;
} else {
colorMap = m_reader->global_colormap;
colorMapSize = m_reader->global_colormap_size;
}
if (!colorMap)
return true;
// Initialize the frame if necessary.
RGBA32Buffer& buffer = m_frameBufferCache[frameIndex];
if ((buffer.status() == RGBA32Buffer::FrameEmpty) && !initFrameBuffer(frameIndex))
return false;
// Write one row's worth of data into the frame.
for (int x = xBegin; x < xEnd; ++x) {
const unsigned char sourceValue = *(rowBuffer + (m_scaled ? m_scaledColumns[x] : x) - frameReader->x_offset);
if ((!frameReader->is_transparent || (sourceValue != frameReader->tpixel)) && (sourceValue < colorMapSize)) {
const size_t colorIndex = static_cast<size_t>(sourceValue) * 3;
buffer.setRGBA(x, yBegin, colorMap[colorIndex], colorMap[colorIndex + 1], colorMap[colorIndex + 2], 255);
} else {
m_currentBufferSawAlpha = true;
// We may or may not need to write transparent pixels to the buffer.
// If we're compositing against a previous image, it's wrong, and if
// we're writing atop a cleared, fully transparent buffer, it's
// unnecessary; but if we're decoding an interlaced gif and
// displaying it "Haeberli"-style, we must write these for passes
// beyond the first, or the initial passes will "show through" the
// later ones.
if (writeTransparentPixels)
buffer.setRGBA(x, yBegin, 0, 0, 0, 0);
}
}
// Tell the frame to copy the row data if need be.
if (repeatCount > 1)
buffer.copyRowNTimes(xBegin, xEnd, yBegin, yEnd);
return true;
}
void GIFImageDecoder::frameComplete(unsigned frameIndex, unsigned frameDuration, RGBA32Buffer::FrameDisposalMethod disposalMethod)
{
// Initialize the frame if necessary. Some GIFs insert do-nothing frames,
// in which case we never reach haveDecodedRow() before getting here.
RGBA32Buffer& buffer = m_frameBufferCache[frameIndex];
if ((buffer.status() == RGBA32Buffer::FrameEmpty) && !initFrameBuffer(frameIndex))
return;
buffer.setStatus(RGBA32Buffer::FrameComplete);
buffer.setDuration(frameDuration);
buffer.setDisposalMethod(disposalMethod);
if (!m_currentBufferSawAlpha) {
// The whole frame was non-transparent, so it's possible that the entire
// resulting buffer was non-transparent, and we can setHasAlpha(false).
if (buffer.rect().contains(IntRect(IntPoint(), scaledSize())))
buffer.setHasAlpha(false);
else if (frameIndex) {
// Tricky case. This frame does not have alpha only if everywhere
// outside its rect doesn't have alpha. To know whether this is
// true, we check the start state of the frame -- if it doesn't have
// alpha, we're safe.
//
// First skip over prior DisposeOverwritePrevious frames (since they
// don't affect the start state of this frame) the same way we do in
// initFrameBuffer().
const RGBA32Buffer* prevBuffer = &m_frameBufferCache[--frameIndex];
while (frameIndex && (prevBuffer->disposalMethod() == RGBA32Buffer::DisposeOverwritePrevious))
prevBuffer = &m_frameBufferCache[--frameIndex];
// Now, if we're at a DisposeNotSpecified or DisposeKeep frame, then
// we can say we have no alpha if that frame had no alpha. But
// since in initFrameBuffer() we already copied that frame's alpha
// state into the current frame's, we need do nothing at all here.
//
// The only remaining case is a DisposeOverwriteBgcolor frame. If
// it had no alpha, and its rect is contained in the current frame's
// rect, we know the current frame has no alpha.
if ((prevBuffer->disposalMethod() == RGBA32Buffer::DisposeOverwriteBgcolor) && !prevBuffer->hasAlpha() && buffer.rect().contains(prevBuffer->rect()))
buffer.setHasAlpha(false);
}
}
}
void GIFImageDecoder::gifComplete()
{
if (m_reader)
m_repetitionCount = m_reader->loop_count;
m_reader.clear();
}
void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query)
{
if (m_failed)
return;
m_failed = !m_reader->read((const unsigned char*)m_data->data() + m_readOffset, m_data->size() - m_readOffset, query, haltAtFrame);
if (m_failed)
m_reader.clear();
}
bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
{
// Initialize the frame rect in our buffer.
const GIFFrameReader* frameReader = m_reader->frame_reader;
IntRect frameRect(frameReader->x_offset, frameReader->y_offset, frameReader->width, frameReader->height);
// Make sure the frameRect doesn't extend outside the buffer.
if (frameRect.right() > size().width())
frameRect.setWidth(size().width() - frameReader->x_offset);
if (frameRect.bottom() > size().height())
frameRect.setHeight(size().height() - frameReader->y_offset);
RGBA32Buffer* const buffer = &m_frameBufferCache[frameIndex];
int left = upperBoundScaledX(frameRect.x());
int right = lowerBoundScaledX(frameRect.right(), left);
int top = upperBoundScaledY(frameRect.y());
int bottom = lowerBoundScaledY(frameRect.bottom(), top);
buffer->setRect(IntRect(left, top, right - left, bottom - top));
if (!frameIndex) {
// This is the first frame, so we're not relying on any previous data.
if (!buffer->setSize(scaledSize().width(), scaledSize().height())) {
m_failed = true;
return false;
}
} else {
// The starting state for this frame depends on the previous frame's
// disposal method.
//
// 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. (If the
// first frame specifies this method, it will get treated like
// DisposeOverwriteBgcolor below and reset to a completely empty image.)
const RGBA32Buffer* prevBuffer = &m_frameBufferCache[--frameIndex];
RGBA32Buffer::FrameDisposalMethod prevMethod = prevBuffer->disposalMethod();
while (frameIndex && (prevMethod == RGBA32Buffer::DisposeOverwritePrevious)) {
prevBuffer = &m_frameBufferCache[--frameIndex];
prevMethod = prevBuffer->disposalMethod();
}
ASSERT(prevBuffer->status() == RGBA32Buffer::FrameComplete);
if ((prevMethod == RGBA32Buffer::DisposeNotSpecified) || (prevMethod == RGBA32Buffer::DisposeKeep)) {
// Preserve the last frame as the starting state for this frame.
buffer->copyBitmapData(*prevBuffer);
} else {
// We want to clear the previous frame to transparent, without
// affecting pixels in the image outside of the frame.
const IntRect& prevRect = prevBuffer->rect();
const IntSize& bufferSize = scaledSize();
if (!frameIndex || prevRect.contains(IntRect(IntPoint(), scaledSize()))) {
// Clearing the first frame, or a frame the size of the whole
// image, results in a completely empty image.
if (!buffer->setSize(bufferSize.width(), bufferSize.height())) {
m_failed = true;
return false;
}
} else {
// Copy the whole previous buffer, then clear just its frame.
buffer->copyBitmapData(*prevBuffer);
for (int y = prevRect.y(); y < prevRect.bottom(); ++y) {
for (int x = prevRect.x(); x < prevRect.right(); ++x)
buffer->setRGBA(x, y, 0, 0, 0, 0);
}
if ((prevRect.width() > 0) && (prevRect.height() > 0))
buffer->setHasAlpha(true);
}
}
}
// Update our status to be partially complete.
buffer->setStatus(RGBA32Buffer::FramePartial);
// Reset the alpha pixel tracker for this frame.
m_currentBufferSawAlpha = false;
return true;
}
} // namespace WebCore
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