GIF decoding to Index8, unit tests and misusing unit test as benchmark

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp

Index: third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
index 07dd9de56970d610b5895b1f6ebbb0dc0d9b8ca7..5527cafcfd98293d59573b405d2f0b9d594ddf23 100644
--- a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
@@ -33,9 +33,12 @@
 
 namespace blink {
 
-GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption colorOptions, size_t maxDecodedBytes)
+GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption colorOptions, size_t maxDecodedBytes, ImageFrame::ColorType colorType)
     : ImageDecoder(alphaOption, colorOptions, maxDecodedBytes)
+    , phaveDecodedRow(&GIFImageDecoder::haveDecodedRowIndex8)
     , m_repetitionCount(cAnimationLoopOnce)
+    , m_colorMode(colorType)
+    , m_forceN32Decoding(false)
 {
 }
 
@@ -102,8 +105,9 @@ bool GIFImageDecoder::setFailed()
     return ImageDecoder::setFailed();
 }
 
-bool GIFImageDecoder::haveDecodedRow(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
+bool GIFImageDecoder::haveDecodedRowN32(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
 {
+    ASSERT(m_colorMode == ImageFrame::N32 || m_forceN32Decoding);
     const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     // The pixel data and coordinates supplied to us are relative to the frame's
     // origin within the entire image size, i.e.
@@ -125,11 +129,7 @@ bool GIFImageDecoder::haveDecodedRow(size_t frameIndex, GIFRow::const_iterator r
 
     GIFColorMap::Table::const_iterator colorTableIter = colorTable.begin();
 
-    // Initialize the frame if necessary.
     ImageFrame& buffer = m_frameBufferCache[frameIndex];
-    if ((buffer.status() == ImageFrame::FrameEmpty) && !initFrameBuffer(frameIndex))
-        return false;
-
     const size_t transparentPixel = frameContext->transparentPixel();
     GIFRow::const_iterator rowEnd = rowBegin + (xEnd - xBegin);
     ImageFrame::PixelData* currentAddress = buffer.getAddr(xBegin, yBegin);
@@ -174,6 +174,73 @@ bool GIFImageDecoder::haveDecodedRow(size_t frameIndex, GIFRow::const_iterator r
     return true;
 }
 
+bool GIFImageDecoder::haveDecodedRowIndex8(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
+{
+    ASSERT(m_colorMode == ImageFrame::Index8 && !m_forceN32Decoding);
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
+    // 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.
+    const int xBegin = frameContext->xOffset();
+    const int yBegin = frameContext->yOffset() + rowNumber;
+    const int xEnd = std::min(static_cast<int>(frameContext->xOffset() + width), size().width());
+    const int yEnd = std::min(static_cast<int>(frameContext->yOffset() + rowNumber + repeatCount), size().height());
+    if (!width || (xBegin < 0) || (yBegin < 0) || (xEnd <= xBegin) || (yEnd <= yBegin))
+        return true;
+
+    const GIFColorMap::Table& colorTable = frameContext->localColorMap().isDefined() ? frameContext->localColorMap().table() : m_reader->globalColorMap().table();
+
+    if (colorTable.isEmpty())
+        return true;
+
+
+    ImageFrame& buffer = m_frameBufferCache[frameIndex];
+    const size_t transparentPixel = frameContext->transparentPixel();
+    GIFRow::const_iterator rowEnd = rowBegin + (xEnd - xBegin);
+    ImageFrame::PixelData8* currentAddress = buffer.getAddr8(xBegin, yBegin);
+
+    bool opaque = true;
+    if (transparentPixel < colorTable.size()) {
+        // writeTransparentPixels is writing without check.
+        writeTransparentPixels = writeTransparentPixels || buffer.requiredPreviousFrameIndex() == kNotFound;
+        if (writeTransparentPixels) {
+            for (; rowBegin != rowEnd;) {
+                opaque = opaque && (*rowBegin ^ transparentPixel);
+                *currentAddress++ = *rowBegin++;
+            }
+        } else {
+            for (; rowBegin != rowEnd; ++rowBegin, ++currentAddress) {
+                size_t index = *rowBegin;
+                if (index == transparentPixel) {
+                    opaque = false;
+                } else {
+                    *currentAddress = index;
+                }
+            }
+        }
+    } else {
+        // No transparency to deal with.
+        for (; rowBegin != rowEnd;)
+            *currentAddress++ = *rowBegin++;
+    }
+
+    m_currentBufferSawAlpha = !opaque;
+
+    // Tell the frame to copy the row data if specified.
+    if (repeatCount > 1) {
+        const int rowBytes = (xEnd - xBegin) * sizeof(uint8_t);
+        const ImageFrame::PixelData8* const startAddr = buffer.getAddr8(xBegin, yBegin);
+        for (int destY = yBegin + 1; destY < yEnd; ++destY)
+            memcpy(buffer.getAddr8(xBegin, destY), startAddr, rowBytes);
+    }
+
+    buffer.setPixelsChanged(true);
+    return true;
+}
+
 bool GIFImageDecoder::parseCompleted() const
 {
     return m_reader && m_reader->parseCompleted();
@@ -264,6 +331,9 @@ void GIFImageDecoder::initializeNewFrame(size_t index)
 
 void GIFImageDecoder::decode(size_t index)
 {
+    phaveDecodedRow = (m_colorMode == ImageFrame::Index8 && !m_forceN32Decoding)
+        ? (&GIFImageDecoder::haveDecodedRowIndex8)
+        : (&GIFImageDecoder::haveDecodedRowN32);
     parse(GIFFrameCountQuery);
 
     if (failed())
@@ -277,9 +347,24 @@ void GIFImageDecoder::decode(size_t index)
     } while (frameToDecode != kNotFound && m_frameBufferCache[frameToDecode].status() != ImageFrame::FrameComplete);
 
     for (auto i = framesToDecode.rbegin(); i != framesToDecode.rend(); ++i) {
+        bool notSuitableForIndex8(m_forceN32Decoding);
         if (!m_reader->decode(*i)) {
-            setFailed();
-            return;
+            // Decoder asks to switch color mode as Index8 is not applicable. Try to decode using N32.
+            // This happens only when transparent pixels showing previous frames or offsets are detected
+            // and table is changed.
+            if (notSuitableForIndex8 != m_forceN32Decoding) {
+                ASSERT(m_colorMode == ImageFrame::Index8);
+                clearFrameBuffer(*i);
+                // N32 decoding would continue until there is non dependent Index8 frame detected, see initFrameBuffer().
+                phaveDecodedRow = &GIFImageDecoder::haveDecodedRowN32;
+                if (!m_reader->decode(*i)) {
+                    setFailed();
+                    return;
+                }
+            } else {
+                setFailed();
+                return;
+            }
         }
 
         // We need more data to continue decoding.
@@ -293,6 +378,15 @@ void GIFImageDecoder::decode(size_t index)
         setFailed();
 }
 
+void GIFImageDecoder::setForceN32Decoding(bool value)
+{
+    ASSERT(m_colorMode == ImageFrame::Index8);
+    m_forceN32Decoding = value;
+    phaveDecodedRow = (!value && m_colorMode == ImageFrame::Index8)
+        ? (&GIFImageDecoder::haveDecodedRowIndex8)
+        : (&GIFImageDecoder::haveDecodedRowN32);
+}
+
 void GIFImageDecoder::parse(GIFParseQuery query)
 {
     if (failed())
@@ -307,7 +401,7 @@ void GIFImageDecoder::parse(GIFParseQuery query)
         setFailed();
 }
 
-bool GIFImageDecoder::initFrameBuffer(size_t frameIndex)
+bool GIFImageDecoder::initFrameBufferN32(size_t frameIndex)
 {
     // Initialize the frame rect in our buffer.
     ImageFrame* const buffer = &m_frameBufferCache[frameIndex];
@@ -342,4 +436,135 @@ bool GIFImageDecoder::initFrameBuffer(size_t frameIndex)
     return true;
 }
 
+static bool framesUseSameColorTable(const GIFFrameContext& frame1, const GIFFrameContext& frame2)
+{
+    auto frame1Local = frame1.localColorMap();
+    auto frame2Local = frame2.localColorMap();
+    bool useFrame1Local = frame1Local.isDefined();
+    bool useFrame2Local = frame2Local.isDefined();
+    if (useFrame1Local != useFrame2Local)
+        return false;
+    size_t transparent1 = frame1.transparentPixel();
+    size_t transparent2 = frame2.transparentPixel();
+    if (!useFrame1Local) {
+        // They both use global ColorMap, check if transparent pixels are the same.
+        ASSERT(!useFrame2Local);
+        return (transparent1 == transparent2);
+    }
+    // Both use local color maps, check if it is the same.
+    return ((frame1Local.getPosition() == frame2Local.getPosition()) && (transparent1 == transparent2));
+}
+
+// Helper method for recomputing if frame decoding has no dependency to previous frames.
+void GIFImageDecoder::updateRequiredPreviousFrame(ImageFrame* buffer, const GIFFrameContext& frameContext)
+{
+    ASSERT(m_colorMode == ImageFrame::Index8);
+    if (buffer->requiredPreviousFrameIndex() == kNotFound)
+        return;
+
+    bool isFullScreen = frameContext.frameRect().contains(IntRect(IntPoint(), size()));
+    const GIFColorMap::Table& colorTable = frameContext.localColorMap().isDefined()
+        ? frameContext.localColorMap().table() : m_reader->globalColorMap().table();
+
+    // If transparent pixel is outside color table, there is no transparent pixel.
+    // e.g. Color table in some of the GIFs is having 40 elements and transparentPixel set to 0xFF.
+    bool opaque = frameContext.transparentPixel() >= colorTable.size();
+
+    // If fullscreen and opaque, the frame is independent of previous frame.
+    if (isFullScreen && opaque)
+        buffer->setRequiredPreviousFrameIndex(kNotFound);
+}
+
+bool GIFImageDecoder::initFrameBuffer(size_t frameIndex)
+{
+    ImageFrame* buffer = &m_frameBufferCache[frameIndex];
+    if (buffer->status() != ImageFrame::FrameEmpty)
+        return true;
+
+    if (m_colorMode == ImageFrame::N32) {
+        return initFrameBufferN32(frameIndex);
+    }
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
+    updateRequiredPreviousFrame(buffer, *frameContext);
+    size_t requiredPreviousFrameIndex = buffer->requiredPreviousFrameIndex();
+
+    if (requiredPreviousFrameIndex == kNotFound) {
+        // This frame doesn't rely on any previous data and it is OK to
+        // switch back from forced N32 to Index8.
+        setForceN32Decoding(false);
+        // phaveDecodedRow = &GIFImageDecoder::haveDecodedRowIndex8;
+        const GIFColorMap::Table& colorTable = frameContext->localColorMap().isDefined()
+            ? frameContext->localColorMap().table() : m_reader->globalColorMap().table();
+        if (!buffer->setSizeIndex8(size().width(), size().height(), colorTable, frameContext->transparentPixel()))
+            return setFailed();
+    } else {
+        const ImageFrame* prevBuffer = &m_frameBufferCache[requiredPreviousFrameIndex];
+        ASSERT(prevBuffer->status() == ImageFrame::FrameComplete);
+
+        // Preserve the last frame as the starting state for this frame.
+        bool useN32 = true;
+        if (!m_forceN32Decoding) {
+            // If color table is different from previous frame and in the same time, there is transparency
+            // or the frame is subrect, cannot do Index8. Otherwise, with the same table, no problem to continue
+            // with Index8 and start decoding from a copy of required frame.
+            if (framesUseSameColorTable(*frameContext, *(m_reader->frameContext(requiredPreviousFrameIndex)))) {
+                useN32 = false;
+                if (!buffer->copyBitmapData(*prevBuffer))
+                    return setFailed();
+                ASSERT(buffer->getSkBitmap().colorType() == kIndex_8_SkColorType);
+            } else {
+                setForceN32Decoding(true);
+                useN32 = true;
+            }
+        }
+        // For unsupported Index8 and N32, next frame starts as previous frame copy to N32.
+        if (useN32 && !buffer->copyBitmapData(*prevBuffer, ImageFrame::N32))
+            return setFailed();
+
+        if (prevBuffer->disposalMethod() == ImageFrame::DisposeOverwriteBgcolor) {
+            // We want to clear the previous frame to transparent, without
+            // affecting pixels in the image outside of the frame.
+            const IntRect& prevRect = prevBuffer->originalFrameRect();
+            ASSERT(!prevRect.contains(IntRect(IntPoint(), size())));
+            buffer->zeroFillFrameRect(prevRect);
+        }
+    }
+
+    // Update our status to be partially complete.
+    buffer->setStatus(ImageFrame::FramePartial);
+
+    // Reset the alpha pixel tracker for this frame.
+    m_currentBufferSawAlpha = false;
+    return true;
+}
+
+bool GIFImageDecoder::canDecodeTo(size_t index, ImageFrame::ColorType outputType)
+{
+    if ((index >= frameCount()) || (m_colorMode == ImageFrame::N32) || failed())
+        return (outputType == m_colorMode);
+
+    // Go from one to previous until calculating if Index8 is supported.
+    size_t frameToDecode = index;
+    ImageFrame::ColorType calculatedOutput = ImageFrame::Index8;
+    while (frameToDecode != kNotFound) {
+        ImageFrame* buffer = &m_frameBufferCache[frameToDecode];
+        if (buffer->status() == ImageFrame::FrameComplete) {
+            // In this case, color type from complete frame is kept.
+            calculatedOutput = static_cast<ImageFrame::ColorType>(buffer->getSkBitmap().colorType());
+            break;
+        }
+        const GIFFrameContext* frameContext = m_reader->frameContext(frameToDecode);
+        updateRequiredPreviousFrame(buffer, *frameContext);
+        if (buffer->requiredPreviousFrameIndex() == kNotFound)
+            break;
+        frameToDecode = m_frameBufferCache[frameToDecode].requiredPreviousFrameIndex();
+        if (frameToDecode != kNotFound && !framesUseSameColorTable(*frameContext, *(m_reader->frameContext(frameToDecode)))) {
+            // If dependent to previous frame and they don't use the same color table, not possible to use Index8.
+            calculatedOutput = ImageFrame::N32;
+            break;
+        }
+    }
+    return (calculatedOutput == outputType);
+}
+
 } // namespace blink