void WEBPImageDecoder::applyPostProcessing(size_t frameIndex)
{
ImageFrame& buffer = m_frameBufferCache[frameIndex];
int width;
int decodedHeight;
if (!WebPIDecGetRGB(m_decoder, &decodedHeight, &width, 0, 0))
return; // See also https://bugs.webkit.org/show_bug.cgi?id=74062
if (decodedHeight <= 0)
return;
const IntRect& frameRect = buffer.originalFrameRect();
ASSERT_WITH_SECURITY_IMPLICATION(width == frameRect.width());
ASSERT_WITH_SECURITY_IMPLICATION(decodedHeight <= frameRect.height());
const int left = frameRect.x();
const int top = frameRect.y();
#if USE(QCMSLIB)
if (qcms_transform* transform = colorTransform()) {
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
const int canvasY = top + y;
uint8_t* row = reinterpret_cast<uint8_t*>(buffer.getAddr(left, canvasY));
qcms_transform_data_type(transform, row, row, width, QCMS_OUTPUT_RGBX);
uint8_t* pixel = row;
for (int x = 0; x < width; ++x, pixel += 4) {
const int canvasX = left + x;
buffer.setRGBA(canvasX, canvasY, pixel[0], pixel[1], pixel[2], pixel[3]);
}
}
}
#endif // USE(QCMSLIB)
// During the decoding of current frame, we may have set some pixels to be transparent (i.e. alpha < 255).
// However, the value of each of these pixels should have been determined by blending it against the value
// of that pixel in the previous frame if alpha blend source was 'BlendAtopPreviousFrame'. So, we correct these
// pixels based on disposal method of the previous frame and the previous frame buffer.
// FIXME: This could be avoided if libwebp decoder had an API that used the previous required frame
// to do the alpha-blending by itself.
if ((m_formatFlags & ANIMATION_FLAG) && frameIndex && buffer.alphaBlendSource() == ImageFrame::BlendAtopPreviousFrame && buffer.requiredPreviousFrameIndex() != kNotFound) {
ImageFrame& prevBuffer = m_frameBufferCache[frameIndex - 1];
ASSERT(prevBuffer.status() == ImageFrame::FrameComplete);
ImageFrame::DisposalMethod prevDisposalMethod = prevBuffer.disposalMethod();
if (prevDisposalMethod == ImageFrame::DisposeKeep) { // Blend transparent pixels with pixels in previous canvas.
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
m_blendFunction(buffer, prevBuffer, top + y, left, width);
}
} else if (prevDisposalMethod == ImageFrame::DisposeOverwriteBgcolor) {
const IntRect& prevRect = prevBuffer.originalFrameRect();
// We need to blend a transparent pixel with its value just after initFrame() call. That is:
// * Blend with fully transparent pixel if it belongs to prevRect <-- This is a no-op.
// * Blend with the pixel in the previous canvas otherwise <-- Needs alpha-blending.
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
int canvasY = top + y;
int left1, width1, left2, width2;
findBlendRangeAtRow(frameRect, prevRect, canvasY, left1, width1, left2, width2);
if (width1 > 0)
m_blendFunction(buffer, prevBuffer, canvasY, left1, width1);
if (width2 > 0)
m_blendFunction(buffer, prevBuffer, canvasY, left2, width2);
}
}
}
m_decodedHeight = decodedHeight;
buffer.setPixelsChanged(true);
}
void WEBPImageDecoder::applyPostProcessing(size_t frameIndex) {
ImageFrame& buffer = m_frameBufferCache[frameIndex];
int width;
int decodedHeight;
if (!WebPIDecGetRGB(m_decoder, &decodedHeight, &width, 0, 0))
return; // See also https://bugs.webkit.org/show_bug.cgi?id=74062
if (decodedHeight <= 0)
return;
const IntRect& frameRect = buffer.originalFrameRect();
SECURITY_DCHECK(width == frameRect.width());
SECURITY_DCHECK(decodedHeight <= frameRect.height());
const int left = frameRect.x();
const int top = frameRect.y();
// TODO (msarett):
// Here we apply the color space transformation to the dst space.
// It does not really make sense to transform to a gamma-encoded
// space and then immediately after, perform a linear premultiply
// and linear blending. Can we find a way to perform the
// premultiplication and blending in a linear space?
SkColorSpaceXform* xform = colorTransform();
if (xform) {
const SkColorSpaceXform::ColorFormat srcFormat =
SkColorSpaceXform::kBGRA_8888_ColorFormat;
const SkColorSpaceXform::ColorFormat dstFormat =
SkColorSpaceXform::kRGBA_8888_ColorFormat;
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
const int canvasY = top + y;
uint8_t* row = reinterpret_cast<uint8_t*>(buffer.getAddr(left, canvasY));
xform->apply(dstFormat, row, srcFormat, row, width,
kUnpremul_SkAlphaType);
uint8_t* pixel = row;
for (int x = 0; x < width; ++x, pixel += 4) {
const int canvasX = left + x;
buffer.setRGBA(canvasX, canvasY, pixel[0], pixel[1], pixel[2],
pixel[3]);
}
}
}
// During the decoding of the current frame, we may have set some pixels to be
// transparent (i.e. alpha < 255). If the alpha blend source was
// 'BlendAtopPreviousFrame', the values of these pixels should be determined
// by blending them against the pixels of the corresponding previous frame.
// Compute the correct opaque values now.
// FIXME: This could be avoided if libwebp decoder had an API that used the
// previous required frame to do the alpha-blending by itself.
if ((m_formatFlags & ANIMATION_FLAG) && frameIndex &&
buffer.getAlphaBlendSource() == ImageFrame::BlendAtopPreviousFrame &&
buffer.requiredPreviousFrameIndex() != kNotFound) {
ImageFrame& prevBuffer = m_frameBufferCache[frameIndex - 1];
ASSERT(prevBuffer.getStatus() == ImageFrame::FrameComplete);
ImageFrame::DisposalMethod prevDisposalMethod =
prevBuffer.getDisposalMethod();
if (prevDisposalMethod == ImageFrame::DisposeKeep) {
// Blend transparent pixels with pixels in previous canvas.
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
m_blendFunction(buffer, prevBuffer, top + y, left, width);
}
} else if (prevDisposalMethod == ImageFrame::DisposeOverwriteBgcolor) {
const IntRect& prevRect = prevBuffer.originalFrameRect();
// We need to blend a transparent pixel with the starting value (from just
// after the initFrame() call). If the pixel belongs to prevRect, the
// starting value was fully transparent, so this is a no-op. Otherwise, we
// need to blend against the pixel from the previous canvas.
for (int y = m_decodedHeight; y < decodedHeight; ++y) {
int canvasY = top + y;
int left1, width1, left2, width2;
findBlendRangeAtRow(frameRect, prevRect, canvasY, left1, width1, left2,
width2);
if (width1 > 0)
m_blendFunction(buffer, prevBuffer, canvasY, left1, width1);
if (width2 > 0)
m_blendFunction(buffer, prevBuffer, canvasY, left2, width2);
}
}
}
m_decodedHeight = decodedHeight;
buffer.setPixelsChanged(true);
}