/* * 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(*m_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); } 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