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/*
* 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.
*/
#include "config.h"
#include "GIFImageDecoder.h"
#include "GIFImageReader.h"
#include <limits>
namespace WebCore {
GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption gammaAndColorProfileOption)
: ScalableImageDecoder(alphaOption, gammaAndColorProfileOption)
{
}
GIFImageDecoder::~GIFImageDecoder() = default;
void GIFImageDecoder::setData(SharedBuffer& data, bool allDataReceived)
{
if (failed())
return;
ScalableImageDecoder::setData(data, allDataReceived);
if (m_reader)
m_reader->setData(&data);
}
bool GIFImageDecoder::setSize(const IntSize& size)
{
if (ScalableImageDecoder::encodedDataStatus() >= EncodedDataStatus::SizeAvailable && this->size() == size)
return true;
return ScalableImageDecoder::setSize(size);
}
size_t GIFImageDecoder::frameCount() const
{
const_cast<GIFImageDecoder*>(this)->decode(std::numeric_limits<unsigned>::max(), GIFFrameCountQuery, isAllDataReceived());
return m_frameBufferCache.size();
}
RepetitionCount 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. If the reader hasn't
// seen a loop count yet, it will return cLoopCountNotSeen, in which case we
// should default to looping once (the initial value for
// |m_repetitionCount|).
//
// There are some additional wrinkles here. First, ImageSource::clear()
// may destroy the reader, making the result from the reader _less_
// authoritative on future calls if the recreated reader hasn't seen the
// loop count. We don't need to special-case this because in this case the
// new reader will once again return cLoopCountNotSeen, and we won't
// overwrite the cached correct value.
//
// Second, a GIF might never set a loop count at all, in which case we
// should continue to treat it as a "loop once" animation. We don't need
// special code here either, because in this case we'll never change
// |m_repetitionCount| from its default value.
//
// Third, we use the same GIFImageReader for counting frames and we might
// see the loop count and then encounter a decoding error which happens
// later in the stream. It is also possible that no frames are in the
// stream. In these cases we should just loop once.
if (failed() || (m_reader && (!m_reader->imagesCount())))
m_repetitionCount = RepetitionCountOnce;
else if (m_reader && m_reader->loopCount() != cLoopCountNotSeen)
m_repetitionCount = m_reader->loopCount() > 0 ? m_reader->loopCount() + 1 : m_reader->loopCount();
return m_repetitionCount;
}
size_t GIFImageDecoder::findFirstRequiredFrameToDecode(size_t frameIndex)
{
// The first frame doesn't depend on any other.
if (!frameIndex)
return 0;
for (size_t i = frameIndex; i > 0; --i) {
auto& frame = m_frameBufferCache[i - 1];
// Frames with disposal method RestoreToPrevious are useless, skip them.
if (frame.disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)
continue;
// At this point the disposal method can be Unspecified, DoNotDispose or RestoreToBackground.
// In every case, if the frame is complete we can start decoding the next one.
if (frame.isComplete())
return i;
// If the disposal method of this frame is RestoreToBackground and it fills the whole area,
// the next frame's backing store is initialized to transparent, so we start decoding with it.
if (frame.disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToBackground) {
// We cannot use frame.backingStore()->frameRect() here, because it has been cleared
// when the frame was removed from the cache. We need to get the values from the
// reader context.
const auto* frameContext = m_reader->frameContext(i - 1);
ASSERT(frameContext);
IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
if (frameRect.contains({ { }, size() }))
return i;
}
}
return 0;
}
ScalableImageDecoderFrame* GIFImageDecoder::frameBufferAtIndex(size_t index)
{
if (index >= frameCount())
return 0;
auto& frame = m_frameBufferCache[index];
if (!frame.isComplete()) {
for (auto i = findFirstRequiredFrameToDecode(index); i <= index; i++)
decode(i + 1, GIFFullQuery, isAllDataReceived());
}
return &frame;
}
bool GIFImageDecoder::setFailed()
{
m_reader = nullptr;
return ScalableImageDecoder::setFailed();
}
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<ScalableImageDecoderFrame>::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 DisposalMethod::RestoreToPrevious, 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 DisposalMethod::RestoreToPrevious, stop
// scanning, as we'll only need this frame when decoding the next one.
Vector<ScalableImageDecoderFrame>::iterator i(end);
for (; (i != m_frameBufferCache.begin()) && (i->isInvalid() || (i->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)); --i) {
if (i->isComplete() && (i != end))
i->clear();
}
// Now |i| holds the last frame we need to preserve; clear prior frames.
for (Vector<ScalableImageDecoderFrame>::iterator j(m_frameBufferCache.begin()); j != i; ++j) {
ASSERT(!j->isPartial());
if (!j->isInvalid())
j->clear();
}
}
bool GIFImageDecoder::haveDecodedRow(unsigned frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
{
const GIFFrameContext* frameContext = m_reader->frameContext();
// The pixel data and coordinates supplied to us are relative to the frame's
// origin within the entire image size, i.e.
// (frameContext->xOffset, frameContext->yOffset). There is no guarantee
// that width == (size().width() - frameContext->xOffset), so
// we must ensure we don't run off the end of either the source data or the
// row's X-coordinates.
int xBegin = frameContext->xOffset;
int yBegin = frameContext->yOffset + rowNumber;
int xEnd = std::min(static_cast<int>(frameContext->xOffset + width), size().width());
int yEnd = std::min(static_cast<int>(frameContext->yOffset + rowNumber + repeatCount), size().height());
if (rowBuffer.isEmpty() || xEnd <= xBegin || yEnd <= yBegin)
return true;
// Get the colormap.
const unsigned char* colorMap;
unsigned colorMapSize;
if (frameContext->isLocalColormapDefined) {
colorMap = m_reader->localColormap(frameContext);
colorMapSize = m_reader->localColormapSize(frameContext);
} else {
colorMap = m_reader->globalColormap();
colorMapSize = m_reader->globalColormapSize();
}
if (!colorMap)
return true;
// Initialize the frame if necessary.
auto& buffer = m_frameBufferCache[frameIndex];
if ((buffer.isInvalid() && !initFrameBuffer(frameIndex)) || !buffer.hasBackingStore())
return false;
auto* currentAddress = buffer.backingStore()->pixelAt(xBegin, yBegin);
// Write one row's worth of data into the frame.
for (int x = xBegin; x < xEnd; ++x) {
const unsigned char sourceValue = rowBuffer[x - frameContext->xOffset];
if ((!frameContext->isTransparent || (sourceValue != frameContext->tpixel)) && (sourceValue < colorMapSize)) {
const size_t colorIndex = static_cast<size_t>(sourceValue) * 3;
buffer.backingStore()->setPixel(currentAddress, 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.backingStore()->setPixel(currentAddress, 0, 0, 0, 0);
}
++currentAddress;
}
// Tell the frame to copy the row data if need be.
if (repeatCount > 1)
buffer.backingStore()->repeatFirstRow(IntRect(xBegin, yBegin, xEnd - xBegin , yEnd - yBegin));
return true;
}
bool GIFImageDecoder::frameComplete(unsigned frameIndex, unsigned frameDuration, ScalableImageDecoderFrame::DisposalMethod disposalMethod)
{
// Initialize the frame if necessary. Some GIFs insert do-nothing frames,
// in which case we never reach haveDecodedRow() before getting here.
auto& buffer = m_frameBufferCache[frameIndex];
if (buffer.isInvalid() && !initFrameBuffer(frameIndex))
return false; // initFrameBuffer() has already called setFailed().
buffer.setDecodingStatus(DecodingStatus::Complete);
buffer.setDuration(Seconds::fromMilliseconds(frameDuration));
buffer.setDisposalMethod(disposalMethod);
if (!m_currentBufferSawAlpha) {
IntRect rect = buffer.backingStore()->frameRect();
// The whole frame was non-transparent, so it's possible that the entire
// resulting buffer was non-transparent, and we can setHasAlpha(false).
if (rect.contains(IntRect(IntPoint(), size())))
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 DisposalMethod::RestoreToPrevious frames (since they
// don't affect the start state of this frame) the same way we do in
// initFrameBuffer().
const auto* prevBuffer = &m_frameBufferCache[--frameIndex];
while (frameIndex && (prevBuffer->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious))
prevBuffer = &m_frameBufferCache[--frameIndex];
// Now, if we're at a DisposalMethod::Unspecified or DisposalMethod::DoNotDispose 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 DisposalMethod::RestoreToBackground 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.
IntRect prevRect = prevBuffer->backingStore()->frameRect();
if ((prevBuffer->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToBackground) && !prevBuffer->hasAlpha() && rect.contains(prevRect))
buffer.setHasAlpha(false);
}
}
return true;
}
void GIFImageDecoder::gifComplete()
{
// Cache the repetition count, which is now as authoritative as it's ever
// going to be.
repetitionCount();
m_reader = nullptr;
}
void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query, bool allDataReceived)
{
if (failed())
return;
if (!m_reader) {
m_reader = makeUnique<GIFImageReader>(this);
m_reader->setData(m_data.get());
}
if (query == GIFSizeQuery) {
if (!m_reader->decode(GIFSizeQuery, haltAtFrame))
setFailed();
return;
}
if (!m_reader->decode(GIFFrameCountQuery, haltAtFrame)) {
setFailed();
return;
}
m_frameBufferCache.resize(m_reader->imagesCount());
if (query == GIFFrameCountQuery)
return;
if (!m_reader->decode(GIFFullQuery, haltAtFrame)) {
setFailed();
return;
}
// It is also a fatal error if all data is received but we failed to decode
// all frames completely.
if (allDataReceived && haltAtFrame >= m_frameBufferCache.size() && m_reader)
setFailed();
}
bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
{
// Initialize the frame rect in our buffer.
const GIFFrameContext* frameContext = m_reader->frameContext();
IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
auto* const buffer = &m_frameBufferCache[frameIndex];
if (!frameIndex) {
// This is the first frame, so we're not relying on any previous data.
if (!buffer->initialize(size(), m_premultiplyAlpha))
return setFailed();
} else {
// The starting state for this frame depends on the previous frame's
// disposal method.
//
// Frames that use the DisposalMethod::RestoreToPrevious 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
// DisposalMethod::RestoreToBackground below and reset to a completely empty image.)
const auto* prevBuffer = &m_frameBufferCache[--frameIndex];
auto prevMethod = prevBuffer->disposalMethod();
while (frameIndex && (prevMethod == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)) {
prevBuffer = &m_frameBufferCache[--frameIndex];
prevMethod = prevBuffer->disposalMethod();
}
ASSERT(prevBuffer->isComplete());
if ((prevMethod == ScalableImageDecoderFrame::DisposalMethod::Unspecified) || (prevMethod == ScalableImageDecoderFrame::DisposalMethod::DoNotDispose)) {
// Preserve the last frame as the starting state for this frame.
if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
return setFailed();
} else {
// We want to clear the previous frame to transparent, without
// affecting pixels in the image outside of the frame.
IntRect prevRect = prevBuffer->backingStore()->frameRect();
const IntSize& bufferSize = size();
if (!frameIndex || prevRect.contains(IntRect(IntPoint(), size()))) {
// Clearing the first frame, or a frame the size of the whole
// image, results in a completely empty image.
if (!buffer->initialize(bufferSize, m_premultiplyAlpha))
return setFailed();
} else {
// Copy the whole previous buffer, then clear just its frame.
if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
return setFailed();
buffer->backingStore()->clearRect(prevRect);
buffer->setHasAlpha(true);
}
}
}
// Make sure the frameRect doesn't extend outside the buffer.
if (frameRect.maxX() > size().width())
frameRect.setWidth(size().width() - frameContext->xOffset);
if (frameRect.maxY() > size().height())
frameRect.setHeight(size().height() - frameContext->yOffset);
buffer->backingStore()->setFrameRect(frameRect);
// Update our status to be partially complete.
buffer->setDecodingStatus(DecodingStatus::Partial);
// Reset the alpha pixel tracker for this frame.
m_currentBufferSawAlpha = false;
return true;
}
} // namespace WebCore