Move gif image decoder to SkCodec

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 357917f67d3cff36f6b0a9e23a76c2d9e9ad86c2..16c295a42f3236f3a21a8a0a8f071feedf15be7c 100644
--- a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp
@@ -25,10 +25,10 @@
 
 #include "platform/image-decoders/gif/GIFImageDecoder.h"
 
-#include "platform/image-decoders/gif/GIFImageReader.h"
+#include <limits>
+#include "third_party/skia/include/core/SkImageInfo.h"
 #include "wtf/NotFound.h"
 #include "wtf/PtrUtil.h"
-#include <limits>
 
 namespace blink {
 
@@ -36,246 +36,244 @@ GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption,
                                  const ColorBehavior& colorBehavior,
                                  size_t maxDecodedBytes)
     : ImageDecoder(alphaOption, colorBehavior, maxDecodedBytes),
-      m_repetitionCount(cAnimationLoopOnce) {}
-
-GIFImageDecoder::~GIFImageDecoder() {}
+      m_codec(),
+      m_segmentStream(nullptr) {}
+
+GIFImageDecoder::~GIFImageDecoder() {
+  if (!m_codec) {
+    // if we did not create m_codec and thus did not pass ownership to it
+    if (m_segmentStream)
+      delete m_segmentStream;
+  }
+}
 
 void GIFImageDecoder::onSetData(SegmentReader* data) {
-  if (m_reader)
-    m_reader->setData(data);
+  if (!data) {
+    if (m_segmentStream)
+      m_segmentStream->setReader(nullptr, false);
+    return;
+  }
+
+  if (!m_segmentStream)
+    m_segmentStream = new SegmentStream();
+
+  m_segmentStream->setReader(data, isAllDataReceived());
+
+  // If we don't have a SkCodec yet, create one from the stream
+  if (!m_codec) {
+    SkCodec* codec = SkCodec::NewFromStream(m_segmentStream);
+    if (codec) {
+      m_codec.reset(codec);
+    } else {
+      // m_segmentStream's ownership is passed. It is deleted if SkCodec
+      // creation fails. In this case, release our reference so we can create a
+      // new SegmentStream later.
+      m_segmentStream = nullptr;
+      return;
+    }
+
+    // SkCodec::NewFromStream will read enough of the image to get the image
+    // size.
+    SkImageInfo imageInfo = m_codec->getInfo();
+    setSize(imageInfo.width(), imageInfo.height());
+  }
 }
 
 int GIFImageDecoder::repetitionCount() const {
+  if (!m_codec)
+    return cAnimationLoopOnce;
+
   // 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.
+  // packets sent back by the webserver) not always.
   //
-  // 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 (isAllDataReceived() && parseCompleted() && m_reader->imagesCount() == 1)
-    m_repetitionCount = cAnimationNone;
-  else if (failed() || (m_reader && (!m_reader->imagesCount())))
-    m_repetitionCount = cAnimationLoopOnce;
-  else if (m_reader && m_reader->loopCount() != cLoopCountNotSeen)
-    m_repetitionCount = m_reader->loopCount();
-  return m_repetitionCount;
-}
-
-bool GIFImageDecoder::frameIsCompleteAtIndex(size_t index) const {
-  return m_reader && (index < m_reader->imagesCount()) &&
-         m_reader->frameContext(index)->isComplete();
-}
+  // SkCodec will parse forward in the file if the repetition count has not been
+  // seen yet.
 
-float GIFImageDecoder::frameDurationAtIndex(size_t index) const {
-  return (m_reader && (index < m_reader->imagesCount()) &&
-          m_reader->frameContext(index)->isHeaderDefined())
-             ? m_reader->frameContext(index)->delayTime()
-             : 0;
-}
-
-bool GIFImageDecoder::setFailed() {
-  m_reader.reset();
-  return ImageDecoder::setFailed();
-}
-
-bool GIFImageDecoder::haveDecodedRow(size_t frameIndex,
-                                     GIFRow::const_iterator rowBegin,
-                                     size_t width,
-                                     size_t rowNumber,
-                                     unsigned repeatCount,
-                                     bool writeTransparentPixels) {
-  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().getTable()
-          : m_reader->globalColorMap().getTable();
-
-  if (colorTable.isEmpty())
-    return true;
-
-  GIFColorMap::Table::const_iterator colorTableIter = colorTable.begin();
-
-  // Initialize the frame if necessary.
-  ImageFrame& buffer = m_frameBufferCache[frameIndex];
-  if (!initFrameBuffer(frameIndex))
-    return false;
-
-  const size_t transparentPixel = frameContext->transparentPixel();
-  GIFRow::const_iterator rowEnd = rowBegin + (xEnd - xBegin);
-  ImageFrame::PixelData* currentAddress = buffer.getAddr(xBegin, yBegin);
-
-  // 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.
-  //
-  // The loops below are almost identical. One writes a transparent pixel
-  // and one doesn't based on the value of |writeTransparentPixels|.
-  // The condition check is taken out of the loop to enhance performance.
-  // This optimization reduces decoding time by about 15% for a 3MB image.
-  if (writeTransparentPixels) {
-    for (; rowBegin != rowEnd; ++rowBegin, ++currentAddress) {
-      const size_t sourceValue = *rowBegin;
-      if ((sourceValue != transparentPixel) &&
-          (sourceValue < colorTable.size())) {
-        *currentAddress = colorTableIter[sourceValue];
-      } else {
-        *currentAddress = 0;
-        m_currentBufferSawAlpha = true;
-      }
-    }
-  } else {
-    for (; rowBegin != rowEnd; ++rowBegin, ++currentAddress) {
-      const size_t sourceValue = *rowBegin;
-      if ((sourceValue != transparentPixel) &&
-          (sourceValue < colorTable.size()))
-        *currentAddress = colorTableIter[sourceValue];
-      else
-        m_currentBufferSawAlpha = true;
-    }
+  std::vector<SkCodec::FrameInfo> frameInfos = m_codec->getFrameInfo();
+  if (isAllDataReceived() && frameInfos.size() == 1)
+    return cAnimationNone;
+  if (failed())
+    return cAnimationLoopOnce;
+
+  int repetitionCount = m_codec->getRepetitionCount();
+  switch (repetitionCount) {
+    case 0:
+      return cAnimationLoopOnce;
+    case SkCodec::kRepetitionCountInfinite:
+      return cAnimationLoopInfinite;
+    default:
+      return repetitionCount;
   }
-
-  // Tell the frame to copy the row data if need be.
-  if (repeatCount > 1)
-    buffer.copyRowNTimes(xBegin, xEnd, yBegin, yEnd);
-
-  buffer.setPixelsChanged(true);
-  return true;
-}
-
-bool GIFImageDecoder::parseCompleted() const {
-  return m_reader && m_reader->parseCompleted();
 }
 
-bool GIFImageDecoder::frameComplete(size_t frameIndex) {
-  // Initialize the frame if necessary.  Some GIFs insert do-nothing frames,
-  // in which case we never reach haveDecodedRow() before getting here.
-  if (!initFrameBuffer(frameIndex))
-    return false;  // initFrameBuffer() has already called setFailed().
+bool GIFImageDecoder::frameIsCompleteAtIndex(size_t index) const {
+  if (!m_codec)
+    return false;
 
-  m_frameBufferCache[frameIndex].setStatus(ImageFrame::FrameComplete);
-  if (!m_currentBufferSawAlpha)
-    correctAlphaWhenFrameBufferSawNoAlpha(frameIndex);
+  std::vector<SkCodec::FrameInfo> frameInfos = m_codec->getFrameInfo();
+  if (frameInfos.size() <= index)
+    return false;
 
-  return true;
+  return frameInfos[index].fFullyReceived;
 }
 
-void GIFImageDecoder::clearFrameBuffer(size_t frameIndex) {
-  if (m_reader &&
-      m_frameBufferCache[frameIndex].getStatus() == ImageFrame::FramePartial) {
-    // Reset the state of the partial frame in the reader so that the frame
-    // can be decoded again when requested.
-    m_reader->clearDecodeState(frameIndex);
-  }
-  ImageDecoder::clearFrameBuffer(frameIndex);
+float GIFImageDecoder::frameDurationAtIndex(size_t index) const {
+  if (index < m_frameBufferCache.size())
+    return m_frameBufferCache[index].duration();
+  return 0;
 }
 
 size_t GIFImageDecoder::decodeFrameCount() {
-  parse(GIFFrameCountQuery);
-  // If decoding fails, |m_reader| will have been destroyed.  Instead of
-  // returning 0 in this case, return the existing number of frames.  This way
-  // if we get halfway through the image before decoding fails, we won't
-  // suddenly start reporting that the image has zero frames.
-  return failed() ? m_frameBufferCache.size() : m_reader->imagesCount();
+  if (!m_codec)
+    return 0;
+
+  std::vector<SkCodec::FrameInfo> frameInfos = m_codec->getFrameInfo();
+  return frameInfos.size();
 }
 
 void GIFImageDecoder::initializeNewFrame(size_t index) {
-  ImageFrame* buffer = &m_frameBufferCache[index];
-  const GIFFrameContext* frameContext = m_reader->frameContext(index);
-  buffer->setOriginalFrameRect(
-      intersection(frameContext->frameRect(), IntRect(IntPoint(), size())));
-  buffer->setDuration(frameContext->delayTime());
-  buffer->setDisposalMethod(frameContext->getDisposalMethod());
-  buffer->setRequiredPreviousFrameIndex(
-      findRequiredPreviousFrame(index, false));
+  DCHECK(m_codec);
+
+  std::vector<SkCodec::FrameInfo> frameInfos = m_codec->getFrameInfo();
+
+  ImageFrame& frame = m_frameBufferCache[index];
+  // SkCodec does not inform us if only a portion of the image was updated
+  // in the current frame. Because of this, rather than correctly filling in
+  // the frame rect, we set the frame rect to be the image's full size.
+  IntSize fullImageSize = size();
+  frame.setOriginalFrameRect(IntRect(IntPoint(), fullImageSize));
+  frame.setDuration(frameInfos[index].fDuration);
+  size_t requiredPreviousFrameIndex = frameInfos[index].fRequiredFrame;
+  if (requiredPreviousFrameIndex == SkCodec::kNone)
+    requiredPreviousFrameIndex = WTF::kNotFound;
+  frame.setRequiredPreviousFrameIndex(requiredPreviousFrameIndex);
+  // The disposal method is not required any more, but is left in place
+  // for the other image decoders that do not yet rely on SkCodec.
+  // For now, fill it with DisposeKeep.
+  frame.setDisposalMethod(ImageFrame::DisposeKeep);
 }
 
 void GIFImageDecoder::decode(size_t index) {
-  parse(GIFFrameCountQuery);
-
   if (failed())
     return;
 
-  updateAggressivePurging(index);
+  if (!m_codec)
+    return;
 
-  Vector<size_t> framesToDecode = findFramesToDecode(index);
-  for (auto i = framesToDecode.rbegin(); i != framesToDecode.rend(); ++i) {
-    if (!m_reader->decode(*i)) {
+  if (m_frameBufferCache.size() <= index) {
+    // It is a fatal error if all data is received and we have decoded all
+    // frames available but the file is truncated.
+    if (isAllDataReceived())
       setFailed();
-      return;
-    }
 
-    // If this returns false, we need more data to continue decoding.
-    if (!postDecodeProcessing(*i))
-      break;
+    return;
   }
 
-  // It is also a fatal error if all data is received and we have decoded all
-  // frames available but the file is truncated.
-  if (index >= m_frameBufferCache.size() - 1 && isAllDataReceived() &&
-      m_reader && !m_reader->parseCompleted())
-    setFailed();
-}
+  updateAggressivePurging(index);
 
-void GIFImageDecoder::parse(GIFParseQuery query) {
-  if (failed())
-    return;
+  SkImageInfo imageInfo = m_codec->getInfo().makeColorType(kN32_SkColorType);
+
+  SkCodec::Options options;
+  options.fFrameIndex = index;
+  options.fHasPriorFrame = false;
+
+  ImageFrame& frame = m_frameBufferCache[index];
+  if (frame.getStatus() == ImageFrame::FrameEmpty) {
+    size_t requiredPreviousFrameIndex = frame.requiredPreviousFrameIndex();
+    if (requiredPreviousFrameIndex == WTF::kNotFound) {
+      frame.setSizeAndColorSpace(size().width(), size().height(),
+                                 colorSpaceForSkImages());
+    } else {
+      ImageFrame& requiredPreviousFrame =
+          m_frameBufferCache[requiredPreviousFrameIndex];
+
+      if (requiredPreviousFrame.getStatus() != ImageFrame::FrameComplete)
+        decode(requiredPreviousFrameIndex);
+
+      // We try to reuse |requiredPreviousFrame| as starting state to avoid
+      // copying. If canReusePreviousFrameBuffer returns false, we must copy
+      // the data since |requiredPreviousFrame| is necessary to decode this
+      // or later frames. In that case copy the data instead.
+      if ((!canReusePreviousFrameBuffer(index) ||
+           !frame.takeBitmapDataIfWritable(&requiredPreviousFrame)) &&
+          !frame.copyBitmapData(requiredPreviousFrame)) {
+        setFailed();
+        return;
+      }
 
-  if (!m_reader) {
-    m_reader = WTF::makeUnique<GIFImageReader>(this);
-    m_reader->setData(m_data);
+      options.fHasPriorFrame = true;
+    }
+
+    SkCodec::Result startIncrementalDecodeResult =
+        m_codec->startIncrementalDecode(imageInfo, frame.bitmap().getPixels(),
+                                        frame.bitmap().rowBytes(), &options,
+                                        nullptr, nullptr);
+    switch (startIncrementalDecodeResult) {
+      case SkCodec::kSuccess:
+        break;
+      case SkCodec::kIncompleteInput:
+        return;
+      default:
+        setFailed();
+        return;
+    }
+    frame.setStatus(ImageFrame::FramePartial);
   }
 
-  if (!m_reader->parse(query))
-    setFailed();
-}
+  int rowsDecoded = 0;
+  SkCodec::Result incrementalDecodeResult =
+      m_codec->incrementalDecode(&rowsDecoded);
+  switch (incrementalDecodeResult) {
+    case SkCodec::kSuccess:
+      frame.setPixelsChanged(true);
+      frame.setStatus(ImageFrame::FrameComplete);
+      postDecodeProcessing(index);
+      break;
+    case SkCodec::kIncompleteInput:
+      // This decoder will not attempt to decode a frame unless it is complete

[scroggo_chromium, 2017/03/08 16:36:10]

Come to think of it, although BitmapImage will not try to decode an incomplete
frame, nothing guarantees that. I think it'd be better to check against
fFullyReceived.

[cblume, 2017/03/08 19:49:43]

Yeah, I think that makes sense.

I also think if (index != 0   might actually be more clear to me. What do you
think? if (index   reads like a pointer being valid to me. Maybe that's just my
old habits.

[scroggo_chromium, 2017/03/08 21:04:11]

I do not have a strong preference here, but noel@ has encouraged me to use e.g.

  if (index)

instead of

  if (index != 0)

The style guide[1] currently accepts both:

"Checks for zero/non-zero can be compared directly to zero if desired, but this
is left to discretion."

but I think I've seen some other changes over time, and I could believe this
guideline has changed. (WebKit prefers the former [2], and this code (and the
style guide, I believe - it looks very similar, too...) comes from WebKit, so
that seems likely. Following WebKit style will likely keep you consistent with
surrounding code.)

[1] https://www.chromium.org/blink/coding-style#TOC-Null-false-and-0
[2] https://webkit.org/code-style-guidelines/#null-false-and-zero

[cblume, 2017/03/08 23:18:57]

Cool. I'll leave it as if (index  :)

[Noel Gordon, 2017/03/09 04:12:28]

Yeah, recent addition.  Reading

   if (index != 0)

one might ask if index is pointer-type (naming style requires indexPtr to make
that case clear) since 0 is another way of saying NULL, etc.  With the style
change that allow both, then we could get lots of 

   if (indexPtr != nullptr)

added to the code base. That'd get boring pretty quick, imho.  It's 

   if ([something convertible to boolean expression])

so anything that truthy or falsey works: integer types, floats, pointer types,
operator() bool, etc.
surrounding code.

Yeah that, be consistent. The style rule (comparisons to 0) was designed to be
simple and easy to remember, save typing, and work in all cases, aka, the
simplest thing that could possibly work (KISS).

   if (index), if (indexPtr), etc.

+      // unless it is frame 0. We should only get this value if:
+      // 1.) we have only part of frame 0, or
+      // 2.) there was an error decoding a frame other than 0
+      //
+      // If we are on frame 0 but all data is received, that is also an error.
+      if (index || isAllDataReceived()) {
+        setFailed();
+        return;
+      }
 
-void GIFImageDecoder::onInitFrameBuffer(size_t frameIndex) {
-  m_currentBufferSawAlpha = false;
+      frame.setPixelsChanged(true);
+      break;
+    default:
+      setFailed();
+      return;
+  }
 }
 
-bool GIFImageDecoder::canReusePreviousFrameBuffer(size_t frameIndex) const {
-  DCHECK(frameIndex < m_frameBufferCache.size());
-  return m_frameBufferCache[frameIndex].getDisposalMethod() !=
-         ImageFrame::DisposeOverwritePrevious;
+bool GIFImageDecoder::canReusePreviousFrameBuffer(size_t index) const {
+  DCHECK(index < m_frameBufferCache.size());
+
+  // If the current frame and the next frame depend on the same frame, we cannot
+  // reuse the old frame. We must preserve it for the next frame.
+  //
+  // However, if the current and next frame depend on different frames then we
+  // know the current frame is the last one to use the frame it depends on. That
+  // means the current frame can reuse the previous frame buffer.
+  //
+  // If we do not have information about the next frame yet, we cannot assume it
+  // is safe to reuse the previous frame buffer.
+
+  if (index + 1 >= m_frameBufferCache.size())
+    return false;
+
+  const ImageFrame& frame = m_frameBufferCache[index];
+  size_t requiredFrameIndex = frame.requiredPreviousFrameIndex();
+
+  const ImageFrame& nextFrame = m_frameBufferCache[index + 1];
+  size_t nextRequiredFrameIndex = nextFrame.requiredPreviousFrameIndex();
+
+  return requiredFrameIndex != nextRequiredFrameIndex;
 }
 
 }  // namespace blink