blob: 6ecd419ea3370f9bc6320579b0c9cb04f9ecff28 [file] [log] [blame]
* Copyright 2015 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkGifCodec_DEFINED
#define SkGifCodec_DEFINED
#include "SkCodec.h"
#include "SkCodecAnimation.h"
#include "SkColorSpace.h"
#include "SkColorTable.h"
#include "SkImageInfo.h"
#include "SkSwizzler.h"
#include "SkGifImageReader.h"
* This class implements the decoding for gif images
class SkGifCodec : public SkCodec {
static bool IsGif(const void*, size_t);
* Assumes IsGif was called and returned true
* Reads enough of the stream to determine the image format
static SkCodec* NewFromStream(SkStream*, Result*);
// Callback for SkGifImageReader when a row is available.
bool haveDecodedRow(int frameIndex, const unsigned char* rowBegin,
int rowNumber, int repeatCount, bool writeTransparentPixels);
* Performs the full gif decode
Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&,
int*) override;
SkEncodedImageFormat onGetEncodedFormat() const override {
return SkEncodedImageFormat::kGIF;
bool onRewind() override;
uint64_t onGetFillValue(const SkImageInfo&) const override;
int onGetFrameCount() override;
bool onGetFrameInfo(int, FrameInfo*) const override;
int onGetRepetitionCount() override;
Result onStartIncrementalDecode(const SkImageInfo& /*dstInfo*/, void*, size_t,
const SkCodec::Options&) override;
Result onIncrementalDecode(int*) override;
const SkFrameHolder* getFrameHolder() const override {
return fReader.get();
* Initializes the color table that we will use for decoding.
* @param dstInfo Contains the requested dst color type.
* @param frameIndex Frame whose color table to use.
void initializeColorTable(const SkImageInfo& dstInfo, int frameIndex);
* Does necessary setup, including setting up the color table and swizzler.
Result prepareToDecode(const SkImageInfo& dstInfo, const Options& opts);
* Initializes the swizzler.
* @param dstInfo Output image information. Dimensions may have been
* adjusted if the image frame size does not match the size
* indicated in the header.
* @param frameIndex Which frame we are decoding. This determines the frameRect
* to use.
void initializeSwizzler(const SkImageInfo& dstInfo, int frameIndex);
SkSampler* getSampler(bool createIfNecessary) override {
return fSwizzler.get();
* Recursive function to decode a frame.
* @param firstAttempt Whether this is the first call to decodeFrame since
* starting. e.g. true in onGetPixels, and true in the
* first call to onIncrementalDecode after calling
* onStartIncrementalDecode.
* When true, this method may have to initialize the
* frame, for example by filling or decoding the prior
* frame.
* @param opts Options for decoding. May be different from
* this->options() for decoding prior frames. Specifies
* the frame to decode and whether the prior frame has
* already been decoded to fDst. If not, and the frame
* is not independent, this method will recursively
* decode the frame it depends on.
* @param rowsDecoded Out-parameter to report the total number of rows
* that have been decoded (or at least written to, if
* it had to fill), including rows decoded by prior
* calls to onIncrementalDecode.
* @return kSuccess if the frame is complete, kIncompleteInput
* otherwise.
Result decodeFrame(bool firstAttempt, const Options& opts, int* rowsDecoded);
* Swizzles and color xforms (if necessary) into dst.
void applyXformRow(const SkImageInfo& dstInfo, void* dst, const uint8_t* src) const;
* Creates an instance of the decoder
* Called only by NewFromStream
* Takes ownership of the SkGifImageReader
SkGifCodec(const SkEncodedInfo&, const SkImageInfo&, SkGifImageReader*);
std::unique_ptr<SkGifImageReader> fReader;
std::unique_ptr<uint8_t[]> fTmpBuffer;
std::unique_ptr<SkSwizzler> fSwizzler;
sk_sp<SkColorTable> fCurrColorTable;
// We may create a dummy table if there is not a Map in the input data. In
// that case, we set this value to false, and we can skip a lot of decoding
// work (which would not be meaningful anyway). We create a "fake"/"dummy"
// one in that case, so the client and the swizzler have something to draw.
bool fCurrColorTableIsReal;
// Whether the background was filled.
bool fFilledBackground;
// True on the first call to onIncrementalDecode. This value is passed to
// decodeFrame.
bool fFirstCallToIncrementalDecode;
void* fDst;
size_t fDstRowBytes;
// Updated inside haveDecodedRow when rows are decoded, unless we filled
// the background, in which case it is set once and left alone.
int fRowsDecoded;
std::unique_ptr<uint32_t[]> fXformBuffer;
typedef SkCodec INHERITED;
#endif // SkGifCodec_DEFINED