Add support for multiple frames in SkCodec
Add an interface to decode frames beyond the first in SkCodec, and
add an implementation for SkGifCodec.
Add getFrameData to SkCodec. This method reads ahead in the stream
to return a vector containing meta data about each frame in the image.
This is not required in order to decode frames beyond the first, but
it allows a client to learn extra information:
- how long the frame should be displayed
- whether a frame should be blended with a prior frame, allowing the
client to provide the prior frame to speed up decoding
Add a new fields to SkCodec::Options:
- fFrameIndex
- fHasPriorFrame
The API is designed so that SkCodec never caches frames. If a
client wants a frame beyond the first, they specify the frame in
Options.fFrameIndex. If the client does not have the
frame's required frame (the frame that this frame must be blended on
top of) cached, they pass false for
Options.fHasPriorFrame. Unless the frame is
independent, the codec will then recursively decode all frames
necessary to decode fFrameIndex. If the client has the required frame
cached, they can put it in the dst they pass to the codec, and the
codec will only draw fFrameIndex onto it.
Replace SkGifCodec's scanline decoding support with progressive
decoding, and update the tests accordingly.
Implement new APIs in SkGifCodec. Instead of using gif_lib, use
GIFImageReader, imported from Chromium (along with its copyright
headers) with the following changes:
- SkGifCodec is now the client
- Replace blink types
- Combine GIFColorMap::buildTable and ::getTable into a method that
creates and returns an SkColorTable
- Input comes from an SkStream, instead of a SegmentReader. Add
SkStreamBuffer, which buffers the (potentially partial) stream in
order to decode progressively.
(FIXME: This requires copying data that previously was read directly
from the SegmentReader. Does this hurt performance? If so, can we
fix it?)
- Remove UMA code
- Instead of reporting screen width and height to the client, allow the
client to query for it
- Fail earlier if the first frame AND screen have size of zero
- Compute required previous frame when adding a new one
- Move GIFParseQuery from GIFImageDecoder to GIFImageReader
- Allow parsing up to a specific frame (to skip parsing the rest of the
stream if a client only wants the first frame)
- Compute whether the first frame has alpha and supports index 8, to
create the SkImageInfo. This happens before reporting that the size
has been decoded.
Add GIFImageDecoder::haveDecodedRow to SkGifCodec, imported from
Chromium (along with its copyright header), with the following changes:
- Add support for sampling
- Use the swizzler
- Keep track of the rows decoded
- Do *not* keep track of whether we've seen alpha
Remove SkCodec::kOutOfOrder_SkScanlineOrder, which was only used by GIF
scanline decoding.
Call onRewind even if there is no stream (SkGifCodec needs to clear its
decoded state so it will decode from the beginning).
Add a method to SkSwizzler to access the offset into the dst, taking
subsetting into account.
Add a GM that animates a GIF.
Add tests for the new APIs.
*** Behavior changes:
* Previously, we reported that an image with a subset frame and no transparent
index was opaque and used the background index (if present) to fill the
background. This is necessary in order to support index 8, but it does not
match viewers/browsers I have seen. Examples:
- Chromium and Gimp render the background transparent
- Firefox, Safari, Linux Image Viewer, Safari Preview clip to the frame (for
a single frame image)
This CL matches Chromium's behavior and renders the background transparent.
This allows us to have consistent behavior across products and simplifies
the code (relative to what we would have to do to continue the old behavior
on Android). It also means that we will no longer support index 8 for some
GIFs.
* Stop checking for GIFSTAMP - all GIFs should be either 89a or 87a.
This matches Chromium. I suspect that bugs would have been reported if valid
GIFs started with "GIFVER" instead of "GIF89a" or "GIF87a" (but did not decode
in Chromium).
*** Future work not included in this CL:
* Move some checks out of haveDecodedRow, since they are the same for the
entire frame e.g.
- intersecting the frameRect with the full image size
- whether there is a color table
* Change when we write transparent pixels
- In some cases, Chromium deemed this unnecessary, but I suspect it is slower
than the fallback case. There will continue to be cases where we should
*not* write them, but for e.g. the first pass where we have already
cleared to transparent (which we may also be able to skip) writing the
transparent pixels will not make anything incorrect.
* Report color type and alpha type per frame
- Depending on alpha values, disposal methods, frame rects, etc, subsequent
frames may have different properties than the first.
* Skip copies of the encoded data
- We copy the encoded data in case the stream is one that cannot be rewound,
so we can parse and then decode (possibly not immediately). For some input
streams, this is unnecessary.
- I was concerned this cause a performance regression, but on average the
new code is faster than the old for the images I tested [1].
- It may cause a performance regression for Chromium, though, where we can
always move back in the stream, so this should be addressed.
Design doc:
https://docs.google.com/a/google.com/document/d/12Qhf9T92MWfdWujQwCIjhCO3sw6pTJB5pJBwDM1T7Kc/
[1] https://docs.google.com/a/google.com/spreadsheets/d/19V-t9BfbFw5eiwBTKA1qOBkZbchjlTC5EIz6HFy-6RI/
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Review-Url: https://codereview.chromium.org/2045293002
diff --git a/tests/CodecAnimTest.cpp b/tests/CodecAnimTest.cpp
new file mode 100644
index 0000000..e0a446f
--- /dev/null
+++ b/tests/CodecAnimTest.cpp
@@ -0,0 +1,141 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCodec.h"
+#include "SkStream.h"
+
+#include "Resources.h"
+#include "Test.h"
+
+#include <initializer_list>
+#include <vector>
+
+DEF_TEST(Codec_frames, r) {
+ static const struct {
+ const char* fName;
+ size_t fFrameCount;
+ // One less than fFramecount, since the first frame is always
+ // independent.
+ std::vector<size_t> fRequiredFrames;
+ // The size of this one should match fFrameCount for animated, empty
+ // otherwise.
+ std::vector<size_t> fDurations;
+ } gRecs[] = {
+ { "box.gif", 1, {}, {} },
+ { "color_wheel.gif", 1, {}, {} },
+ { "test640x479.gif", 4, { 0, 1, 2 }, { 200, 200, 200, 200 } },
+
+ { "arrow.png", 1, {}, {} },
+ { "google_chrome.ico", 1, {}, {} },
+ { "brickwork-texture.jpg", 1, {}, {} },
+#if defined(SK_CODEC_DECODES_RAW) && (!defined(_WIN32))
+ { "dng_with_preview.dng", 1, {}, {} },
+#endif
+ { "mandrill.wbmp", 1, {}, {} },
+ { "randPixels.bmp", 1, {}, {} },
+ { "yellow_rose.webp", 1, {}, {} },
+ };
+
+ for (auto rec : gRecs) {
+ std::unique_ptr<SkStream> stream(GetResourceAsStream(rec.fName));
+ if (!stream) {
+ // Useful error statement, but sometimes people run tests without
+ // resources, and they do not want to see these messages.
+ //ERRORF(r, "Missing resources? Could not find '%s'", rec.fName);
+ continue;
+ }
+
+ std::unique_ptr<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
+ if (!codec) {
+ ERRORF(r, "Failed to create an SkCodec from '%s'", rec.fName);
+ continue;
+ }
+
+ const size_t expected = rec.fFrameCount;
+ const auto frameInfos = codec->getFrameInfo();
+ // getFrameInfo returns empty set for non-animated.
+ const size_t frameCount = frameInfos.size() == 0 ? 1 : frameInfos.size();
+ if (frameCount != expected) {
+ ERRORF(r, "'%s' expected frame count: %i\tactual: %i", rec.fName, expected, frameCount);
+ continue;
+ }
+
+ if (rec.fRequiredFrames.size() + 1 != expected) {
+ ERRORF(r, "'%s' has wrong number entries in fRequiredFrames; expected: %i\tactual: %i",
+ rec.fName, expected, rec.fRequiredFrames.size());
+ continue;
+ }
+
+ if (1 == frameCount) {
+ continue;
+ }
+
+ // From here on, we are only concerned with animated images.
+ REPORTER_ASSERT(r, frameInfos[0].fRequiredFrame == SkCodec::kNone);
+ for (size_t i = 1; i < frameCount; i++) {
+ REPORTER_ASSERT(r, rec.fRequiredFrames[i-1] == frameInfos[i].fRequiredFrame);
+ }
+
+ // Compare decoding in two ways:
+ // 1. Provide the frame that a frame depends on, so the codec just has to blend.
+ // (in the array cachedFrames)
+ // 2. Do not provide the frame that a frame depends on, so the codec has to decode all the
+ // way back to a key-frame. (in a local variable uncachedFrame)
+ // The two should look the same.
+ std::vector<SkBitmap> cachedFrames(frameCount);
+ const auto& info = codec->getInfo().makeColorType(kN32_SkColorType);
+
+ auto decode = [&](SkBitmap* bm, bool cached, size_t index) {
+ bm->allocPixels(info);
+ if (cached) {
+ // First copy the pixels from the cached frame
+ const size_t requiredFrame = frameInfos[index].fRequiredFrame;
+ if (requiredFrame != SkCodec::kNone) {
+ const bool success = cachedFrames[requiredFrame].copyTo(bm);
+ REPORTER_ASSERT(r, success);
+ }
+ }
+ SkCodec::Options opts;
+ opts.fFrameIndex = index;
+ opts.fHasPriorFrame = cached;
+ const SkCodec::Result result = codec->getPixels(info, bm->getPixels(), bm->rowBytes(),
+ &opts, nullptr, nullptr);
+ REPORTER_ASSERT(r, result == SkCodec::kSuccess);
+ };
+
+ for (size_t i = 0; i < frameCount; i++) {
+ SkBitmap& cachedFrame = cachedFrames[i];
+ decode(&cachedFrame, true, i);
+ SkBitmap uncachedFrame;
+ decode(&uncachedFrame, false, i);
+
+ // Now verify they're equal.
+ const size_t rowLen = info.bytesPerPixel() * info.width();
+ for (int y = 0; y < info.height(); y++) {
+ const void* cachedAddr = cachedFrame.getAddr(0, y);
+ SkASSERT(cachedAddr != nullptr);
+ const void* uncachedAddr = uncachedFrame.getAddr(0, y);
+ SkASSERT(uncachedAddr != nullptr);
+ const bool lineMatches = memcmp(cachedAddr, uncachedAddr, rowLen) == 0;
+ if (!lineMatches) {
+ ERRORF(r, "%s's frame %i is different depending on caching!", rec.fName, i);
+ break;
+ }
+ }
+ }
+
+ if (rec.fDurations.size() != expected) {
+ ERRORF(r, "'%s' has wrong number entries in fDurations; expected: %i\tactual: %i",
+ rec.fName, expected, rec.fDurations.size());
+ continue;
+ }
+
+ for (size_t i = 0; i < frameCount; i++) {
+ REPORTER_ASSERT(r, rec.fDurations[i] == frameInfos[i].fDuration);
+ }
+ }
+}