Add tests for PNGImageDecoder.

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 "platform/image-decoders/ImageDecoderTestHelpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include <memory>
+
+namespace blink {
+
+namespace {
+
+std::unique_ptr<ImageDecoder> createDecoder(
+    ImageDecoder::AlphaOption alphaOption) {
+  return wrapUnique(
+      new PNGImageDecoder(alphaOption, ImageDecoder::ColorSpaceTransformed,
+                          ImageDecoder::targetColorSpaceForTesting(),
+                          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 testRepetitionCount(const char* pngFile, int expectedRepetitionCount) {
+  auto decoder = createDecoderWithPngData(pngFile);
+  // Decoding the frame count sets the repetition count as well.
+  decoder->frameCount();
+  EXPECT_FALSE(decoder->failed());
+  EXPECT_EQ(expectedRepetitionCount, decoder->repetitionCount());
+}
+
+// Verify that the decoder can successfully decode the first frame when
+// initially only half of the frame data is received, resulting in a partially
+// decoded image, and then the rest of the image data is received. Verify that
+// the bitmap hashes of the two stages are different. Also verify that the final
+// bitmap hash is equivalent to the hash when all data is provided at once.
+//
+// This verifies that decoder correctly keeps track of where it stopped
+// decoding when the image was not yet fully received.
+void testProgressiveDecodingContinuesAfterFullData(const char* pngFile,
+                                                   size_t offsetMidFirstFrame) {
+  auto fullData = readFile(pngFile);
+  ASSERT_FALSE(fullData->isEmpty());
+
+  auto decoderUpfront = createDecoder();
+  decoderUpfront->setData(fullData.get(), true);
+  EXPECT_GE(1u, decoderUpfront->frameCount());
+  ImageFrame* frameUpfront = decoderUpfront->frameBufferAtIndex(0);
+  ASSERT_EQ(ImageFrame::FrameComplete, frameUpfront->getStatus());
+  unsigned hashUpfront = hashBitmap(frameUpfront->bitmap());
+
+  auto decoder = createDecoder();
+  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);
+  EXPECT_EQ(hashFull, hashUpfront);
+}
+
+// This test verifies that the frame buffer contents change when progressively
+// decoding the first frame. It should change once for every row in the frame
+// rect. If |offsetFirstFrameEnd| == 0, the test uses the full data size of the
+// image for progressive decoding.
+void testProgressiveDecodingChangesFrameBuffer(const char* pngFile,
+                                               size_t offsetFirstFrameEnd = 0) {
+  auto fullData = readFile(pngFile);
+  ASSERT_FALSE(fullData->isEmpty());
+
+  // First find the height of the frame rect of the first frame.
+  auto sizeDecoder = createDecoder();
+  sizeDecoder->setData(fullData.get(), true);
+  EXPECT_GE(1u, sizeDecoder->frameCount());
+  ImageFrame* frame = sizeDecoder->frameBufferAtIndex(0);
+  ASSERT_EQ(ImageFrame::FrameComplete, frame->getStatus());
+  size_t frameRectRows = frame->originalFrameRect().height();

[scroggo_chromium, 2016/12/05 18:41:29]

nit: could be const.

[joostouwerling, 2016/12/05 19:05:01]

Done. (and some others).

+
+  if (offsetFirstFrameEnd == 0)
+    offsetFirstFrameEnd = fullData->size();
+
+  size_t numTimesBufferChanged = 0;
+  unsigned prevHash;
+  auto decoder = createDecoder();
+  bool frameSeen = false;
+
+  for (size_t length = 1; length <= offsetFirstFrameEnd; length++) {
+    RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(), length);
+    decoder->setData(data, false);
+    frame = decoder->frameBufferAtIndex(0);
+    if (!frame)
+      continue;
+
+    // Initialize |prevHash| at the first time we have a valid frame pointer.
+    // This makes sure we don't count going from "nothing" to an empty frame.

[scroggo_chromium, 2016/12/05 18:41:29]

I don't think that the concern is that we count it. The concern is that we
compare to an uninitialized variable.

[joostouwerling, 2016/12/05 19:05:01]

Hmm, maybe as well, but doesn't comment about uninitialized values only makes
sense when you've seen the other patch? Making sure that we did not have an off
by one error is important for the semantics of this test method.

[scroggo_chromium, 2016/12/05 19:17:20]

I don't think so. It explains why the variable frameSeen exists at all.

+    if (!frameSeen) {
+      prevHash = hashBitmap(frame->bitmap());
+      frameSeen = true;
+      continue;
+    }
+    unsigned newHash = hashBitmap(frame->bitmap());
+    if (newHash != prevHash) {
+      prevHash = newHash;
+      numTimesBufferChanged++;
+    }
+  }
+  EXPECT_EQ(ImageFrame::FrameComplete, frame->getStatus());
+  EXPECT_EQ(numTimesBufferChanged, frameRectRows);

[scroggo_chromium, 2016/12/05 18:41:29]

This is probably true in a lot of cases (e.g. the simple PNG you run the test
on), but it's not guaranteed to be true for all PNGs. Depending on how well a
PNG compresses, a single byte might correspond to more than one row. (From [1]:

"""
the maximum zlib compression is
1:1032, so 1 byte can expand to 1032 bytes.  The shortest PNG encoded (but
not compressed) row is 2 bytes, so you could see another 515 complete rows
after a call to png_process_data_pause, at up to 64 bytes per (transformed)
row.  (The byte count gets worse for longer rows; you might see an
additional 65920 bytes of output row data in the limiting case of a 8240
pixel wide monochome image!)
"""

[1] https://sourceforge.net/p/png-mng/mailman/message/35047667/
)

[joostouwerling, 2016/12/05 19:05:01]

Ah, yeah, so we can either make it a precondition that the provided image has at
most one row per byte, or we omit this test. The latter is probably fine, since
it is similar to testProgressiveDecodingContinuesAfterFullData, like you said.
Done this in the new patch.

+}
+
+// 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
+  // successful parse, since frame data is not analyzed in that step, but
+  // 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
+
+// Static PNG tests
+
+TEST(StaticPNGTests, repetitionCountTest) {
+  testRepetitionCount("/LayoutTests/images/resources/png-simple.png",
+                      cAnimationNone);
+}
+
+TEST(StaticPNGTests, sizeTest) {
+  testSize("/LayoutTests/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/images/resources/png-simple.png");
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_EQ(expectedDuration, decoder->frameDurationAtIndex(0));
+}
+
+TEST(StaticPNGTests, ProgressiveDecoding) {
+  testProgressiveDecoding(&createDecoder,
+                          "/LayoutTests/images/resources/png-simple.png", 11u);
+}
+
+TEST(StaticPNGTests, ProgressiveDecodingChangesFrameBuffer) {
+  testProgressiveDecodingChangesFrameBuffer(
+      "/LayoutTests/images/resources/png-simple.png");
+}
+
+TEST(StaticPNGTests, ProgressiveDecodingContinuesAfterFullData) {
+  testProgressiveDecodingContinuesAfterFullData(
+      "/LayoutTests/images/resources/png-simple.png", 1000u);
+}
+
+TEST(StaticPNGTests, FailureDuringDecodingInvalidatesDecoder) {
+  testFailureDuringDecode(
+      "/LayoutTests/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
+}
+
+// For static images, frameIsCompleteAtIndex(0) should return true if and only
+// if the frame is successfully decoded, not when it is fully received.
+TEST(StaticPNGTests, VerifyFrameCompleteBehavior) {
+  auto decoder =
+      createDecoderWithPngData("/LayoutTests/images/resources/png-simple.png");
+  EXPECT_EQ(1u, decoder->frameCount());
+  EXPECT_FALSE(decoder->frameIsCompleteAtIndex(0));
+  EXPECT_EQ(ImageFrame::FrameComplete,
+            decoder->frameBufferAtIndex(0)->getStatus());
+  EXPECT_TRUE(decoder->frameIsCompleteAtIndex(0));
+}
+
+};  // namespace blink