WIP: Implement APNG

third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "platform/image-decoders/png/PNGImageDecoder.h"
+
+#include "png.h"
+#include "platform/image-decoders/ImageDecoderTestHelpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include <memory>
+
+// The image /LT/f/i/r/png-animated-idat-part-of-animation.png is modified in

[scroggo_chromium, 2016/11/29 16:30:52]

Is this abbreviation standard? If not, I think it would be better to spell out
the path.

[joostouwerling, 2016/12/02 16:08:42]

Vim uses this way of abbreviation, but besides that, no. Changed it.

+// multiple tests to simulate erroneous PNGs. As a reference, the table below
+// shows how the file is structured.
+//
+// Offset | 8     33    95    133   172   210   241   279   314   352   422
+// -------------------------------------------------------------------------
+// Chunk  | IHDR  acTL  fcTL  IDAT  fcTL  fdAT  fcTL  fdAT  fcTL  fdAT  IEND
+//
+// In between the acTL and fcTL there are two other chunks, PLTE and tRNS, but
+// those are not specifically used in this test suite. The same holds for a
+// tEXT chunk in between the last fdAT and IEND.
+//
+// In the current behavior of PNG image decoders, the 4 frames are detected when
+// respectively 141, 249, 322 and 430 bytes are received. The first frame should
+// be detected when the IDAT has been received, and non-first frames when the
+// next fcTL or IEND chunk has been received. Note that all offsets are +8,
+// because a chunk is identified by byte 4-7.
+
+// @TODO(joostouwerling) verify IEND before IDAT fails the decode.
+// @TODO(joostouwerling) extend test image set with other image encodings, such
+//                       as first frame fcTL and multiple chunks per frame.
+
+namespace blink {
+
+namespace {
+
+std::unique_ptr<ImageDecoder> createDecoder(ImageDecoder::AlphaOption alphaOption)
+{
+  return wrapUnique(new PNGImageDecoder(alphaOption,
+                                        ImageDecoder::ColorSpaceApplied,
+                                        ImageDecoder::noDecodedImageByteLimit));
+}
+
+std::unique_ptr<ImageDecoder> createDecoder()
+{
+  return createDecoder(ImageDecoder::AlphaNotPremultiplied);
+}
+
+std::unique_ptr<ImageDecoder> createDecoderWithPngData(const char* pngFile)
+{
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  EXPECT_FALSE(data->isEmpty());
+  decoder->setData(data.get(), true);
+  return decoder;
+}
+
+void testSize(const char* pngFile, IntSize expectedSize)
+{
+  auto decoder = createDecoderWithPngData(pngFile);
+  EXPECT_TRUE(decoder->isSizeAvailable());
+  EXPECT_EQ(expectedSize, decoder->size());
+}
+
+void writeUint32(uint32_t val, png_byte* data)
+{
+  data[0] = val >> 24;
+  data[1] = val >> 16;
+  data[2] = val >> 8;
+  data[3] = val;
+}
+
+void testRepetitionCount(const char* pngFile, int expectedRepetitionCount)
+{
+  auto decoder = createDecoderWithPngData(pngFile);
+  // Decode frame count should see the number of repetitions as well.
+  decoder->frameCount();
+  EXPECT_FALSE(decoder->failed());
+  EXPECT_EQ(expectedRepetitionCount, decoder->repetitionCount());
+}
+
+// Test whether querying for the size of the image works if we present the
+// data byte by byte.
+void testSizeByteByByte(const char *pngFile, size_t bytesNeededToDecodeSize,
+                        IntSize expectedSize)
+{
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+  ASSERT_LT(bytesNeededToDecodeSize, data->size());
+
+  for (size_t length = 1; length <= bytesNeededToDecodeSize; length++) {
+    RefPtr<SharedBuffer> tempData = SharedBuffer::create(data->data(),
+                                                         length);
+    decoder->setData(tempData.get(), false);
+
+    if (length < bytesNeededToDecodeSize) {
+      EXPECT_FALSE(decoder->isSizeAvailable());
+      EXPECT_TRUE(decoder->size().isEmpty());
+      EXPECT_FALSE(decoder->failed());
+    } else {
+      EXPECT_TRUE(decoder->isSizeAvailable());
+      EXPECT_EQ(expectedSize, decoder->size());
+    }
+  }
+  EXPECT_FALSE(decoder->failed());
+}
+
+struct PublicFrameInfo {
+  size_t duration;
+  IntRect frameRect;
+  ImageFrame::AlphaBlendSource alphaBlend;
+  ImageFrame::DisposalMethod disposalMethod;
+};
+
+// This is the frame data for the following PNG image:
+// /LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png
+static PublicFrameInfo pngAnimatedFrameInfo[] = {
+  {500,  {IntPoint(0, 0), IntSize(5, 5)}, ImageFrame::BlendAtopBgcolor,
+    ImageFrame::DisposeKeep},
+  {900,  {IntPoint(1, 1), IntSize(3, 1)}, ImageFrame::BlendAtopBgcolor,
+    ImageFrame::DisposeOverwriteBgcolor},
+  {2000, {IntPoint(1, 2), IntSize(3, 2)}, ImageFrame::BlendAtopPreviousFrame,
+    ImageFrame::DisposeKeep},
+  {1500, {IntPoint(1, 2), IntSize(3, 1)}, ImageFrame::BlendAtopBgcolor,
+    ImageFrame::DisposeKeep},
+};
+
+void compareFrameWithExpectation(const PublicFrameInfo& expected,
+                                 const ImageFrame* frame)
+{
+  EXPECT_EQ(expected.duration, frame->duration());
+  EXPECT_EQ(expected.frameRect, frame->originalFrameRect());
+  EXPECT_EQ(expected.disposalMethod, frame->getDisposalMethod());
+  EXPECT_EQ(expected.alphaBlend, frame->getAlphaBlendSource());
+}
+
+// This function removes |length| bytes at |offset|, and then calls frameCount.
+// It assumes the missing bytes should result in a failed decode because the
+// parser jumps |length| bytes too far in the next chunk.
+void testMissingDataBreaksDecoding(const char* pngFile, size_t offset,
+                                   size_t length)
+{
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+  
+  RefPtr<SharedBuffer> invalidData = SharedBuffer::create(data->data(),
+                                                          offset);
+  invalidData->append(SharedBuffer::create(data->data() + offset + length,
+                                           data->size() - offset - length));
+  ASSERT_EQ(data->size() - length,  invalidData->size());
+
+  decoder->setData(invalidData, true);
+  decoder->frameCount();
+  EXPECT_TRUE(decoder->failed());
+}
+
+// Decoding up to the indicated fcTL offset and then provide an fcTL with
+// the wrong chunk size (20 instead of 26). It should break the decoder.
+void testInvalidFctlSize(const char* pngFile,
+                         size_t offsetFctl,
+                         size_t expectedFrameCountBeforeFail,
+                         bool expectedDecoderFailure)
+{
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+
+  auto decoder = createDecoder();
+  RefPtr<SharedBuffer> invalidData = SharedBuffer::create(data->data(),
+                                                          offsetFctl);
+  
+  // Test if this gives the correct frame count, before the fcTL is parsed.
+  decoder->setData(invalidData, false);
+  EXPECT_EQ(expectedFrameCountBeforeFail, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+
+  // Append the wrong size to the data stream
+  png_byte sizeChunk[4];
+  writeUint32(20, sizeChunk);
+  invalidData->append(reinterpret_cast<char*>(sizeChunk), 4u);
+  
+  // Skip the size in the original data, but provide the rest of the fcTL, 
+  // which is 4B of tag, 26B of data and 4B of CRC, totalling 34B.
+  invalidData->append(data->data() + offsetFctl + 4, 34u);
+
+  decoder->setData(invalidData, false);
+  decoder->frameCount();
+  EXPECT_EQ(expectedDecoderFailure, decoder->failed());
+}
+
+void testDifferentActlFrameCountIsIgnored(const char* pngFile,
+                                          size_t offsetActl,
+                                          size_t injectedFrameCount,
+                                          size_t expectedFrameCount)
+{
+  // First make sure that this tests makes sense.
+  ASSERT_NE(injectedFrameCount, expectedFrameCount);
+
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+  
+  RefPtr<SharedBuffer> diffActlData = SharedBuffer::create(data->data(),
+                                                           offsetActl + 8);
+  // Write the injectedFrameCount to the stream
+  png_byte sizeChunk[4];
+  writeUint32(injectedFrameCount, sizeChunk);
+  diffActlData->append(reinterpret_cast<char*>(sizeChunk), 4u);
+  // Append the rest of the data. The first |offsetActl + 12| bytes that are
+  // already in diffActlData should not be appended again.
+  diffActlData->append(data->data() + offsetActl + 12,
+                       data->size() - offsetActl - 12);
+  
+  decoder->setData(diffActlData, true);
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+}
+
+// Test if the frame bitmap hashes of truncated decoding are equal to the 
+// hashes found by incremental decoding.
+void testProgressiveDecoding(const char *pngFile)
+{
+  RefPtr<SharedBuffer> fullData = readFile(pngFile);
+  ASSERT_TRUE(fullData.get());
+  const size_t fullLength = fullData->size();
+
+  std::unique_ptr<ImageDecoder> decoder;
+  ImageFrame* frame;
+
+  Vector<unsigned> truncatedHashes;
+  Vector<unsigned> progressiveHashes;
+
+  // Compute hashes when the file is truncated.
+  const size_t increment = 13;
+  for (size_t i = 1; i <= fullLength; i += increment) {
+    decoder = createDecoder();
+    RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(), i);
+    decoder->setData(data.get(), i == fullLength);
+    size_t frameCount = decoder->frameCount();
+    ASSERT_FALSE(decoder->failed());
+    if (frameCount == 0) {
+      truncatedHashes.append(0);
+      continue;
+    }
+    frame = decoder->frameBufferAtIndex(frameCount - 1);
+    if (!frame) {
+      truncatedHashes.append(0);
+      continue;
+    }
+    truncatedHashes.append(hashBitmap(frame->bitmap()));
+  }
+
+  // Compute hashes when the file is progressively decoded.
+  decoder = createDecoder();
+  for (size_t i = 1; i <= fullLength; i += increment) {
+    RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(), i);
+    decoder->setData(data.get(), i == fullLength);
+    ASSERT_FALSE(decoder->failed());
+    size_t frameCount = decoder->frameCount();
+    if (frameCount == 0) {
+      progressiveHashes.append(0);
+      continue;
+    }
+    frame = decoder->frameBufferAtIndex(frameCount - 1);
+    if (!frame) {
+      progressiveHashes.append(0);
+      continue;
+    }
+    progressiveHashes.append(hashBitmap(frame->bitmap()));
+  }
+
+  for (size_t i = 0; i < truncatedHashes.size(); ++i)
+    ASSERT_EQ(truncatedHashes[i], progressiveHashes[i]);
+}
+
+// Check that providing the full data after the first frame was partially
+// decoded properly continues where it left off.
+void testProgressiveDecodingContinuesAfterFullData(const char* pngFile,
+                                                   size_t offsetMidFirstFrame)
+{
+  auto fullData = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(fullData->isEmpty());
+  
+  RefPtr<SharedBuffer> partialData =
+      SharedBuffer::create(fullData->data(), offsetMidFirstFrame);
+  decoder->setData(partialData, false);
+
+  EXPECT_EQ(1u, decoder->frameCount());
+  ImageFrame* frame = decoder->frameBufferAtIndex(0);
+  EXPECT_EQ(frame->getStatus(), ImageFrame::FramePartial);
+  unsigned hashPartial = hashBitmap(frame->bitmap());
+
+  decoder->setData(fullData.get(), true);
+  frame = decoder->frameBufferAtIndex(0);
+  EXPECT_EQ(frame->getStatus(), ImageFrame::FrameComplete);
+  unsigned hashFull = hashBitmap(frame->bitmap());
+
+  EXPECT_FALSE(decoder->failed());
+  EXPECT_NE(hashFull, hashPartial);
+}
+
+// This test verifies that the frame buffer contents change when progressively
+// decoding the first frame. It should change more than 1 time: once for the
+// first data, and at least once more thereafter. If |offsetFirstFrameEnd| == 0,
+// the test uses the full data size of the image for its value.
+void testProgressiveDecodingChangesFrameBuffer(const char* pngFile,
+                                               size_t offsetFirstFrameEnd,
+                                               size_t step = 1u)
+{
+  auto fullData = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(fullData->isEmpty());
+  
+  if (offsetFirstFrameEnd == 0)
+    offsetFirstFrameEnd = fullData->size();
+  
+  size_t numTimesBufferChanged = 0;
+  unsigned lastHash;
+
+  for (size_t length = 1; length <= offsetFirstFrameEnd; length += step) {
+    RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(),
+                                                     length);
+    decoder->setData(data, false);
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    if (!frame)
+      continue;
+    unsigned newHash = hashBitmap(frame->bitmap());
+    if (newHash != lastHash) {
+      lastHash = newHash;
+      numTimesBufferChanged++;
+    }
+  }
+  EXPECT_GT(numTimesBufferChanged, 1u);
+}
+
+// @TODO(joostouwerling) Pull this up to ImageDecoderTestHelper since it is also
+//                       used in WEBPImageDecoderTest
+void testRandomDecodeAfterClearFrameBufferCache(const char* pngFile) {
+  SCOPED_TRACE(pngFile);
+
+  RefPtr<SharedBuffer> data = readFile(pngFile);
+  ASSERT_TRUE(data.get());
+  Vector<unsigned> baselineHashes;
+  createDecodingBaseline(&createDecoder, data.get(), &baselineHashes);
+  size_t frameCount = baselineHashes.size();
+
+  std::unique_ptr<ImageDecoder> decoder = createDecoder();
+  decoder->setData(data.get(), true);
+  for (size_t clearExceptFrame = 0; clearExceptFrame < frameCount;
+       ++clearExceptFrame) {
+    decoder->clearCacheExceptFrame(clearExceptFrame);
+    const size_t skippingStep = 2;
+    for (size_t i = 0; i < skippingStep; ++i) {
+      for (size_t j = 0; j < frameCount; j += skippingStep) {
+        SCOPED_TRACE(testing::Message() << "Random i:" << i << " j:" << j);
+        ImageFrame* frame = decoder->frameBufferAtIndex(j);
+        EXPECT_EQ(baselineHashes[j], hashBitmap(frame->bitmap()));
+      }
+    }
+  }
+}
+
+uint32_t premultiplyColor(uint32_t c) {
+  return SkPremultiplyARGBInline(SkGetPackedA32(c), SkGetPackedR32(c),
+                                 SkGetPackedG32(c), SkGetPackedB32(c));
+}
+
+void verifyFramesMatch(const char* pngFile,
+                       const ImageFrame* const a,
+                       ImageFrame* const b) {
+  const SkBitmap& bitmapA = a->bitmap();
+  const SkBitmap& bitmapB = b->bitmap();
+  ASSERT_EQ(bitmapA.width(), bitmapB.width());
+  ASSERT_EQ(bitmapA.height(), bitmapB.height());
+
+  int maxDifference = 0;
+  for (int y = 0; y < bitmapA.height(); ++y) {
+    for (int x = 0; x < bitmapA.width(); ++x) {
+      uint32_t colorA = *bitmapA.getAddr32(x, y);
+      if (!a->premultiplyAlpha())
+        colorA = premultiplyColor(colorA);
+      uint32_t colorB = *bitmapB.getAddr32(x, y);
+      if (!b->premultiplyAlpha())
+        colorB = premultiplyColor(colorB);
+      uint8_t* pixelA = reinterpret_cast<uint8_t*>(&colorA);
+      uint8_t* pixelB = reinterpret_cast<uint8_t*>(&colorB);
+      for (int channel = 0; channel < 4; ++channel) {
+        const int difference = abs(pixelA[channel] - pixelB[channel]);
+        if (difference > maxDifference)
+          maxDifference = difference;
+      }
+    }
+  }
+
+  // Pre-multiplication could round the RGBA channel values. So, we declare
+  // that the frames match if the RGBA channel values differ by at most 2.
+  EXPECT_GE(2, maxDifference) << pngFile;
+}
+
+// Verifies that result of alpha blending is similar for AlphaPremultiplied and
+// AlphaNotPremultiplied cases.
+void testAlphaBlending(const char* pngFile) {
+  RefPtr<SharedBuffer> data = readFile(pngFile);
+  ASSERT_TRUE(data.get());
+
+  std::unique_ptr<ImageDecoder> decoderA =
+      createDecoder(ImageDecoder::AlphaPremultiplied);
+  decoderA->setData(data.get(), true);
+
+  std::unique_ptr<ImageDecoder> decoderB =
+      createDecoder(ImageDecoder::AlphaNotPremultiplied);
+  decoderB->setData(data.get(), true);
+
+  size_t frameCount = decoderA->frameCount();
+  ASSERT_EQ(frameCount, decoderB->frameCount());
+
+  for (size_t i = 0; i < frameCount; ++i)
+    verifyFramesMatch(pngFile, decoderA->frameBufferAtIndex(i),
+                      decoderB->frameBufferAtIndex(i));
+}
+
+// Modify the frame data bytes for frame |frameIndex| so that decoding fails.
+// Parsing should work fine, and is checked with |expectedFrameCountBefore|. If
+// the failure should invalidate the decoder, |expectFailure| should be set to
+// true. If not, |expectedFrameCountAfter| should indicate the new frame count
+// after the failure.
+void testFailureDuringDecode(const char *file,
+                             size_t idatOffset,
+                             size_t frameIndex,
+                             bool expectFailure,
+                             size_t expectedFrameCountBefore,
+                             size_t expectedFrameCountAfter = 0u)
+{ 
+  RefPtr<SharedBuffer> fullData = readFile(file);
+  ASSERT_FALSE(fullData->isEmpty());
+ 
+  // This is the offset where the frame data chunk frame |frameIndex| starts.
+  RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(),
+                                                   idatOffset + 8u);
+  // Repeat the first 8 bytes of the frame data. This should result in a
+  // succesfull parse, since frame data is not analyzed in that step, but

[scroggo_chromium, 2016/11/29 16:30:52]

successful* (two "s"s, one "l")

[joostouwerling, 2016/12/02 16:08:42]

Done.

+  // should give an error during decoding.
+  data->append(fullData->data() + idatOffset, 8u);
+  data->append(fullData->data() + idatOffset + 16u,
+               fullData->size() - idatOffset - 16u);
+
+  auto decoder = createDecoder();
+  decoder->setData(data.get(), true);
+
+  EXPECT_EQ(expectedFrameCountBefore, decoder->frameCount());
+
+  const ImageFrame* const frame = decoder->frameBufferAtIndex(frameIndex);
+  EXPECT_EQ(expectFailure, decoder->failed());
+  if (!expectFailure) {
+    EXPECT_EQ(expectedFrameCountAfter, decoder->frameCount());
+    EXPECT_EQ(ImageFrame::FrameEmpty, frame->getStatus());
+  }
+}
+
+} // Anonymous namespace
+
+// Animated PNG Tests
+
+TEST(AnimatedPNGTests, sizeTest)
+{
+  testSize("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png", IntSize(5, 5));
+  testSize("/LayoutTests/fast/images/resources/png-animated-idat-not-part-of-animation.png", IntSize(227, 35));
+}
+
+TEST(AnimatedPNGTests, repetitionCountTest)
+{
+  testRepetitionCount("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png", 7u);
+  // This is an "animated" image with only one frame, that is, the IDAT is
+  // ignored and there is one fdAT frame. so it should be considered
+  // non-animated.
+  testRepetitionCount("/LayoutTests/fast/images/resources/png-animated-idat-not-part-of-animation.png", cAnimationNone);
+}
+
+// Test if the decoded metdata corresponds to the defined expectations
+TEST(AnimatedPNGTests, MetaDataTest)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  constexpr size_t expectedFrameCount = 4;
+
+  auto decoder = createDecoderWithPngData(pngFile);
+  ASSERT_EQ(expectedFrameCount, decoder->frameCount());
+  for (size_t i = 0; i < expectedFrameCount; i++)
+    compareFrameWithExpectation(pngAnimatedFrameInfo[i],
+                                decoder->frameBufferAtIndex(i));
+}
+
+TEST(AnimatedPNGTests, ByteByByteSizeAvailable)
+{
+  testSizeByteByByte("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+                     141u, IntSize(5, 5));
+  testSizeByteByByte("/LayoutTests/fast/images/resources/png-animated-idat-not-part-of-animation.png",
+                     79u, IntSize(227, 35));
+}
+
+// Test whether the frame metadata decoding also works when we provide the data
+// byte by byte. This should cover the case when the client does not provide
+// all data at once. At given offsets, we expect frames to become available.
+// This test checks whether that is the case, and if so, if the frame data is
+// equal to what we expected.
+TEST(AnimatedPNGTests, ByteByByteMetaData)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  constexpr size_t expectedFrameCount = 4;
+
+  // These are the byte offsets where each frame should have been parsed.
+  // It boils down to the offset of the first fcTL / IEND after the last
+  // frame data chunk, plus 8 bytes for recognition. The exception on this is
+  // the first frame, which is reported when its first framedata is seen.
+  size_t frameOffsets[expectedFrameCount] = {141, 249, 322, 430};
+
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+  size_t framesParsed = 0;
+
+  for (size_t length = 1; length <= frameOffsets[expectedFrameCount - 1]; length++) {
+    RefPtr<SharedBuffer> tempData = SharedBuffer::create(data->data(),
+                                                         length);
+    decoder->setData(tempData.get(), false);
+    EXPECT_FALSE(decoder->failed());
+    if (length < frameOffsets[framesParsed]) {
+      EXPECT_EQ(framesParsed, decoder->frameCount());
+    } else {
+      ASSERT_EQ(framesParsed + 1, decoder->frameCount());
+      compareFrameWithExpectation(pngAnimatedFrameInfo[framesParsed],
+                                  decoder->frameBufferAtIndex(framesParsed));
+      framesParsed++;
+    }
+  }
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+TEST(AnimatedPNGTests, TestRandomFrameDecode)
+{
+  RefPtr<SharedBuffer> fullData = readFile("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+  ASSERT_TRUE(fullData.get());
+  Vector<unsigned> baselineHashes;
+  createDecodingBaseline(&createDecoder, fullData.get(), &baselineHashes);
+  size_t frameCount = baselineHashes.size();
+
+  // Random decoding should get the same results as sequential decoding.
+  std::unique_ptr<ImageDecoder> decoder = createDecoder();
+  decoder->setData(fullData.get(), true);
+  const size_t skippingStep = 2;
+  for (size_t i = 0; i < skippingStep; ++i) {
+    for (size_t j = i; j < frameCount; j += skippingStep) {
+      SCOPED_TRACE(testing::Message() << "Random i:" << i << " j:" << j);
+      ImageFrame* frame = decoder->frameBufferAtIndex(j);
+      EXPECT_EQ(baselineHashes[j], hashBitmap(frame->bitmap()));
+    }
+  }
+
+  // Decoding in reverse order.
+  decoder = createDecoder();
+  decoder->setData(fullData.get(), true);
+  for (size_t i = frameCount; i; --i) {
+    SCOPED_TRACE(testing::Message() << "Reverse i:" << i);
+    ImageFrame* frame = decoder->frameBufferAtIndex(i - 1);
+    EXPECT_EQ(baselineHashes[i - 1], hashBitmap(frame->bitmap()));
+  }
+
+}
+
+TEST(AnimatedPNGTests, TestDecodeAfterReallocation)
+{
+  std::unique_ptr<ImageDecoder> decoder = createDecoder();
+  RefPtr<SharedBuffer> data = readFile("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+  ASSERT_TRUE(data.get());
+
+  // Parse from |data|.
+  decoder->setData(data.get(), true);
+  size_t frameCount = decoder->frameCount();
+
+  // ... and then decode frames from |reallocatedData|.
+  RefPtr<SharedBuffer> reallocatedData = data.get()->copy();
+  ASSERT_TRUE(reallocatedData.get());
+  data.clear();
+  decoder->setData(reallocatedData.get(), true);
+
+  for (size_t i = 0; i < frameCount; ++i) {
+    const ImageFrame* const frame = decoder->frameBufferAtIndex(i);
+    EXPECT_EQ(ImageFrame::FrameComplete, frame->getStatus());
+  }
+}
+
+TEST(AnimatedPNGTests, ProgressiveDecode)
+{
+  testProgressiveDecoding("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+}
+
+TEST(AnimatedPNGTests, ParseAndDecodeByteByByte)
+{
+  testByteByByteDecode(&createDecoder,
+             "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+             4u, 7u);
+}
+
+TEST(AnimatedPNGTests, FailureDuringParsing)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+
+  // Test the first fcTL in the stream. Because no frame data has been set at
+  // this point, the expected frame count is zero. 95 bytes is just before the
+  // first fcTL chunk, at which the first frame is detected. The decoder should
+  // be in the failed state since no frames were parsed before this error.
+  testInvalidFctlSize("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+                      95u, 0u, true);
+  
+  // Test for the third fcTL in the stream. This should be tested as well, 
+  // since the first fcTL is parsed in PNGImageReader::parseSize() whereas
+  // later fcTLs are parsed in PNGImageReader::parse() as part of framecount.
+  // The expected frame count before the fcTL chunk is 1u, since the second
+  // frame is registered when the third fcTL (or IEND) is seen.
+  //
+  // This should *not* set the decoder to the failed state since the first
+  // frame was succesfully parsed, and we still want to show that frame.
+  testInvalidFctlSize("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+                      241u, 1u, false);
+
+}
+
+TEST(AnimatedPNGTests, FailureDuringParsingDueToMissingFctlData)
+{
+  // The fcTL chunk starts at 95u, add 10u to get to the content data, and
+  // remove 5 bytes of data. This sets the decoder to the failed state since
+  // no frames were parsed yet.
+  testMissingDataBreaksDecoding(
+    "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+    105u, 5u);
+}
+
+TEST(AnimatedPNGTests, MissingActlResultsInNonAnimated)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+  
+  // Remove the acTL chunk from the stream.
+  size_t offsetActl = 33;
+  RefPtr<SharedBuffer> noActlData = SharedBuffer::create(data->data(),
+                                                         offsetActl);
+  noActlData->append(data->data() + offsetActl + 20,
+                     data->size() - offsetActl - 20);
+
+  decoder->setData(noActlData, true); 
+  EXPECT_EQ(1u, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+// Test if the indicated frame count by the acTL is ignored if the actual
+// number of frames is different. Test for higher and lower indicated number.
+TEST(AnimatedPNGTests, differentActlFrameCountIsIgnored)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  testDifferentActlFrameCountIsIgnored(pngFile, 33u, 2u, 4u);
+  testDifferentActlFrameCountIsIgnored(pngFile, 33u, 8u, 4u);
+}
+
+// Check if a frame rectangle, that is larger than the image width, gets
+// clipped correctly.
+// @TODO(joostouwerling) use an image that also has data that needs to be
+//                       clipped, not just report larger dimensions.
+// @TODO(joostouwerling) determine how libpng handles larger / smaller images
+//                       than indicated.
+TEST(AnimatedPNGTests, frameRectIsClipped)
+{
+  const char* pngFile = "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+  
+  // Change the width and height of the frame so it falls outside the image.
+  size_t offsetThirdFctl = 241 + 12;
+  RefPtr<SharedBuffer> modifiedData = SharedBuffer::create(data->data(),
+                                                           offsetThirdFctl);
+  png_byte sizeChunk[8];
+  writeUint32(10, sizeChunk);
+  writeUint32(15, sizeChunk + 4);
+  modifiedData->append(const_cast<const char*>(
+                         reinterpret_cast<char*>(sizeChunk)), 8u);
+  modifiedData->append(data->data() + offsetThirdFctl + 8,
+                       data->size() - offsetThirdFctl - 8);
+
+  decoder->setData(modifiedData, true); 
+
+  IntSize expectedSize(5, 5);
+  size_t expectedFrameCount = 4;
+  IntRect expectedFrameRect(IntPoint(1, 2), IntSize(4, 3));
+
+  EXPECT_TRUE(decoder->isSizeAvailable());
+  EXPECT_EQ(expectedSize, decoder->size());
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+  EXPECT_EQ(expectedFrameRect,
+            decoder->frameBufferAtIndex(2)->originalFrameRect());
+}
+
+TEST(AnimatedPNGTests, ProgressiveDecodingChangesFrameBuffer)
+{
+  testProgressiveDecodingChangesFrameBuffer(
+    "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png", 249u);
+}
+
+TEST(AnimatedPNGTests, ProgressiveDecodingContinuesAfterFullData)
+{
+  // 160u is a randomly chosen offset in the IDAT chunk of the first frame.
+  testProgressiveDecodingContinuesAfterFullData(
+    "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png", 160u);
+}
+
+TEST(AnimatedPNGTests, RandomDecodeAfterClearFrameBufferCache)
+{
+  testRandomDecodeAfterClearFrameBufferCache(
+    "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+}
+
+TEST(AnimatedPNGTests, VerifyAlphaBlending) {
+        testAlphaBlending(
+    "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+}
+
+// This tests if the frame count gets set correctly when parsing frameCount 
+// fails in one of the parsing queries.
+//
+// First, enough data is provided such that two frames should be registered.
+// The decoder should at this point not be in the failed status.
+//
+// Then, we provide the rest of the data except for the last IEND chunk, but
+// tell the decoder that this is all the data we have.  The frame count should
+// be three, since one extra frame should be discovered. The fourth frame
+// should *not* be registered since the reader should not be able to determine
+// where the frame ends. The decoder should *not* be in the failed state since
+// there are three frames which can be shown.
+TEST(AnimatedPNGTests, FailureMissingIendChunk) 
+{
+  RefPtr<SharedBuffer> fullData = readFile("/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png");
+  ASSERT_FALSE(fullData->isEmpty());
+  auto decoder = createDecoder();
+  
+  const size_t offsetTwoFrames = 249;
+  const size_t expectedFramesAfter249Bytes = 2;
+  RefPtr<SharedBuffer> tempData = SharedBuffer::create(fullData->data(),
+                                                       offsetTwoFrames);
+  decoder->setData(tempData.get(), false);
+  EXPECT_EQ(expectedFramesAfter249Bytes, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+  
+  // Provide the rest of the data except for the last IEND chunk.
+  const size_t expectedFramesAfterAllExpect12Bytes = 3;
+  tempData = SharedBuffer::create(fullData->data(), fullData->size() - 12);
+  decoder->setData(tempData.get(), true);
+  EXPECT_EQ(expectedFramesAfterAllExpect12Bytes, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+TEST(AnimatedPNGTests, VerifyFrameCountChangesOnDecodingFailure)
+{
+  testFailureDuringDecode(
+      "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+      279u,   // idat offset for frame index 2
+      2u,     // try to decode frame index 2
+      false,  // expect the decoder to *not* be invalidated after the failure
+      4u,     // expected frame count before failure
+      2u);    // expected frame count after failure
+
+  testFailureDuringDecode(
+      "/LayoutTests/fast/images/resources/png-animated-idat-part-of-animation.png",
+      133u,   // idat offset for frame index 0
+      0u,     // try to decode frame index 0
+      true,   // expect the decoder to be invalidated after the failure
+      4u);    // expected frame count before failure
+}
+
+// Static PNG tests
+
+TEST(StaticPNGTests, repetitionCountTest)
+{
+  testRepetitionCount("/LayoutTests/fast/images/resources/png-simple.png",
+                      cAnimationNone);
+}
+
+TEST(StaticPNGTests, sizeTest)
+{
+  testSize("/LayoutTests/fast/images/resources/png-simple.png",
+           IntSize(111, 29));
+}
+
+TEST(StaticPNGTests, MetaDataTest)
+{
+  const size_t expectedFrameCount = 1;
+  const size_t expectedDuration = 0;
+  auto decoder = createDecoderWithPngData("/LayoutTests/fast/images/resources/png-simple.png");
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_EQ(expectedDuration, decoder->frameDurationAtIndex(0));
+}
+
+TEST(StaticPNGTests, InvalidIHDRChunk)
+{
+  testMissingDataBreaksDecoding(
+    "/LayoutTests/fast/images/resources/png-simple.png", 20u, 2u);
+} 
+
+TEST(StaticPNGTests, ProgressiveDecoding)
+{
+  testProgressiveDecoding("/LayoutTests/fast/images/resources/png-simple.png");
+}
+
+TEST(StaticPNGTests, ProgressiveDecodingChangesFrameBuffer)
+{
+  testProgressiveDecodingChangesFrameBuffer(
+    "/LayoutTests/fast/images/resources/png-simple.png", 0u, 5u);
+}
+
+TEST(StaticPNGTests, ProgressiveDecodingContinuesAfterFullData)
+{
+  testProgressiveDecodingContinuesAfterFullData(
+    "/LayoutTests/fast/images/resources/png-simple.png", 1000u);
+}
+
+TEST(StaticPNGTests, FailureDuringDecodingInvalidatesDecoder)
+{
+  testFailureDuringDecode(
+      "/LayoutTests/fast/images/resources/png-simple.png",
+      85u,    // idat offset for frame index 0
+      0u,     // try to decode frame index 0
+      true,   // expect the decoder to be invalidated after the failure
+      1u);    // expected frame count before failure
+}
+
+}; // namespace blink