blob: 4df419057448d547af80542201d74fbd964257b6 [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.
*/
#include "include/codec/SkCodec.h"
#include "include/core/SkColorSpace.h"
#include "include/core/SkData.h"
#include "include/private/SkHalf.h"
#include "src/codec/SkBmpCodec.h"
#include "src/codec/SkCodecPriv.h"
#include "src/codec/SkFrameHolder.h"
#ifdef SK_HAS_HEIF_LIBRARY
#include "src/codec/SkHeifCodec.h"
#endif
#include "src/codec/SkIcoCodec.h"
#include "src/codec/SkJpegCodec.h"
#ifdef SK_HAS_PNG_LIBRARY
#include "src/codec/SkPngCodec.h"
#endif
#include "include/core/SkStream.h"
#include "src/codec/SkRawCodec.h"
#include "src/codec/SkWbmpCodec.h"
#include "src/codec/SkWebpCodec.h"
#ifdef SK_HAS_WUFFS_LIBRARY
#include "src/codec/SkWuffsCodec.h"
#else
#include "src/codec/SkGifCodec.h"
#endif
struct DecoderProc {
bool (*IsFormat)(const void*, size_t);
std::unique_ptr<SkCodec> (*MakeFromStream)(std::unique_ptr<SkStream>, SkCodec::Result*);
};
static std::vector<DecoderProc>* decoders() {
static auto* decoders = new std::vector<DecoderProc> {
#ifdef SK_HAS_JPEG_LIBRARY
{ SkJpegCodec::IsJpeg, SkJpegCodec::MakeFromStream },
#endif
#ifdef SK_HAS_WEBP_LIBRARY
{ SkWebpCodec::IsWebp, SkWebpCodec::MakeFromStream },
#endif
#ifdef SK_HAS_WUFFS_LIBRARY
{ SkWuffsCodec_IsFormat, SkWuffsCodec_MakeFromStream },
#else
{ SkGifCodec::IsGif, SkGifCodec::MakeFromStream },
#endif
#ifdef SK_HAS_PNG_LIBRARY
{ SkIcoCodec::IsIco, SkIcoCodec::MakeFromStream },
#endif
{ SkBmpCodec::IsBmp, SkBmpCodec::MakeFromStream },
{ SkWbmpCodec::IsWbmp, SkWbmpCodec::MakeFromStream },
};
return decoders;
}
void SkCodec::Register(
bool (*peek)(const void*, size_t),
std::unique_ptr<SkCodec> (*make)(std::unique_ptr<SkStream>, SkCodec::Result*)) {
decoders()->push_back(DecoderProc{peek, make});
}
std::unique_ptr<SkCodec> SkCodec::MakeFromStream(
std::unique_ptr<SkStream> stream, Result* outResult,
SkPngChunkReader* chunkReader, SelectionPolicy selectionPolicy) {
Result resultStorage;
if (!outResult) {
outResult = &resultStorage;
}
if (!stream) {
*outResult = kInvalidInput;
return nullptr;
}
if (selectionPolicy != SelectionPolicy::kPreferStillImage
&& selectionPolicy != SelectionPolicy::kPreferAnimation) {
*outResult = kInvalidParameters;
return nullptr;
}
constexpr size_t bytesToRead = MinBufferedBytesNeeded();
char buffer[bytesToRead];
size_t bytesRead = stream->peek(buffer, bytesToRead);
// It is also possible to have a complete image less than bytesToRead bytes
// (e.g. a 1 x 1 wbmp), meaning peek() would return less than bytesToRead.
// Assume that if bytesRead < bytesToRead, but > 0, the stream is shorter
// than bytesToRead, so pass that directly to the decoder.
// It also is possible the stream uses too small a buffer for peeking, but
// we trust the caller to use a large enough buffer.
if (0 == bytesRead) {
// TODO: After implementing peek in CreateJavaOutputStreamAdaptor.cpp, this
// printf could be useful to notice failures.
// SkCodecPrintf("Encoded image data failed to peek!\n");
// It is possible the stream does not support peeking, but does support
// rewinding.
// Attempt to read() and pass the actual amount read to the decoder.
bytesRead = stream->read(buffer, bytesToRead);
if (!stream->rewind()) {
SkCodecPrintf("Encoded image data could not peek or rewind to determine format!\n");
*outResult = kCouldNotRewind;
return nullptr;
}
}
// PNG is special, since we want to be able to supply an SkPngChunkReader.
// But this code follows the same pattern as the loop.
#ifdef SK_HAS_PNG_LIBRARY
if (SkPngCodec::IsPng(buffer, bytesRead)) {
return SkPngCodec::MakeFromStream(std::move(stream), outResult, chunkReader);
} else
#endif
{
for (DecoderProc proc : *decoders()) {
if (proc.IsFormat(buffer, bytesRead)) {
return proc.MakeFromStream(std::move(stream), outResult);
}
}
#ifdef SK_HAS_HEIF_LIBRARY
if (SkHeifCodec::IsHeif(buffer, bytesRead)) {
return SkHeifCodec::MakeFromStream(std::move(stream), selectionPolicy, outResult);
}
#endif
#ifdef SK_CODEC_DECODES_RAW
// Try to treat the input as RAW if all the other checks failed.
return SkRawCodec::MakeFromStream(std::move(stream), outResult);
#endif
}
if (bytesRead < bytesToRead) {
*outResult = kIncompleteInput;
} else {
*outResult = kUnimplemented;
}
return nullptr;
}
std::unique_ptr<SkCodec> SkCodec::MakeFromData(sk_sp<SkData> data, SkPngChunkReader* reader) {
if (!data) {
return nullptr;
}
return MakeFromStream(SkMemoryStream::Make(std::move(data)), nullptr, reader);
}
SkCodec::SkCodec(SkEncodedInfo&& info, XformFormat srcFormat, std::unique_ptr<SkStream> stream,
SkEncodedOrigin origin)
: fEncodedInfo(std::move(info))
, fSrcXformFormat(srcFormat)
, fStream(std::move(stream))
, fNeedsRewind(false)
, fOrigin(origin)
, fDstInfo()
, fOptions()
, fCurrScanline(-1)
, fStartedIncrementalDecode(false)
{}
SkCodec::~SkCodec() {}
bool SkCodec::conversionSupported(const SkImageInfo& dst, bool srcIsOpaque, bool needsColorXform) {
if (!valid_alpha(dst.alphaType(), srcIsOpaque)) {
return false;
}
switch (dst.colorType()) {
case kRGBA_8888_SkColorType:
case kBGRA_8888_SkColorType:
return true;
case kRGBA_F16_SkColorType:
return dst.colorSpace();
case kRGB_565_SkColorType:
return srcIsOpaque;
case kGray_8_SkColorType:
return SkEncodedInfo::kGray_Color == fEncodedInfo.color() && srcIsOpaque;
case kAlpha_8_SkColorType:
// conceptually we can convert anything into alpha_8, but we haven't actually coded
// all of those other conversions yet.
return SkEncodedInfo::kXAlpha_Color == fEncodedInfo.color();
default:
return false;
}
}
bool SkCodec::rewindIfNeeded() {
// Store the value of fNeedsRewind so we can update it. Next read will
// require a rewind.
const bool needsRewind = fNeedsRewind;
fNeedsRewind = true;
if (!needsRewind) {
return true;
}
// startScanlineDecode will need to be called before decoding scanlines.
fCurrScanline = -1;
// startIncrementalDecode will need to be called before incrementalDecode.
fStartedIncrementalDecode = false;
// Some codecs do not have a stream. They may hold onto their own data or another codec.
// They must handle rewinding themselves.
if (fStream && !fStream->rewind()) {
return false;
}
return this->onRewind();
}
static SkIRect frame_rect_on_screen(SkIRect frameRect,
const SkIRect& screenRect) {
if (!frameRect.intersect(screenRect)) {
return SkIRect::MakeEmpty();
}
return frameRect;
}
bool zero_rect(const SkImageInfo& dstInfo, void* pixels, size_t rowBytes,
SkISize srcDimensions, SkIRect prevRect) {
prevRect = frame_rect_on_screen(prevRect, SkIRect::MakeSize(srcDimensions));
if (prevRect.isEmpty()) {
return true;
}
const auto dimensions = dstInfo.dimensions();
if (dimensions != srcDimensions) {
SkRect src = SkRect::Make(srcDimensions);
SkRect dst = SkRect::Make(dimensions);
SkMatrix map = SkMatrix::MakeRectToRect(src, dst, SkMatrix::kCenter_ScaleToFit);
SkRect asRect = SkRect::Make(prevRect);
if (!map.mapRect(&asRect)) {
return false;
}
asRect.roundIn(&prevRect);
if (prevRect.isEmpty()) {
// Down-scaling shrank the empty portion to nothing,
// so nothing to zero.
return true;
}
}
const SkImageInfo info = dstInfo.makeDimensions(prevRect.size());
const size_t bpp = dstInfo.bytesPerPixel();
const size_t offset = prevRect.x() * bpp + prevRect.y() * rowBytes;
void* eraseDst = SkTAddOffset<void>(pixels, offset);
SkSampler::Fill(info, eraseDst, rowBytes, SkCodec::kNo_ZeroInitialized);
return true;
}
SkCodec::Result SkCodec::handleFrameIndex(const SkImageInfo& info, void* pixels, size_t rowBytes,
const Options& options) {
const int index = options.fFrameIndex;
if (0 == index) {
return this->initializeColorXform(info, fEncodedInfo.alpha(), fEncodedInfo.opaque())
? kSuccess : kInvalidConversion;
}
if (index < 0) {
return kInvalidParameters;
}
if (options.fSubset) {
// If we add support for this, we need to update the code that zeroes
// a kRestoreBGColor frame.
return kInvalidParameters;
}
if (index >= this->onGetFrameCount()) {
return kIncompleteInput;
}
const auto* frameHolder = this->getFrameHolder();
SkASSERT(frameHolder);
const auto* frame = frameHolder->getFrame(index);
SkASSERT(frame);
const int requiredFrame = frame->getRequiredFrame();
if (requiredFrame != kNoFrame) {
if (options.fPriorFrame != kNoFrame) {
// Check for a valid frame as a starting point. Alternatively, we could
// treat an invalid frame as not providing one, but rejecting it will
// make it easier to catch the mistake.
if (options.fPriorFrame < requiredFrame || options.fPriorFrame >= index) {
return kInvalidParameters;
}
const auto* prevFrame = frameHolder->getFrame(options.fPriorFrame);
switch (prevFrame->getDisposalMethod()) {
case SkCodecAnimation::DisposalMethod::kRestorePrevious:
return kInvalidParameters;
case SkCodecAnimation::DisposalMethod::kRestoreBGColor:
// If a frame after the required frame is provided, there is no
// need to clear, since it must be covered by the desired frame.
if (options.fPriorFrame == requiredFrame) {
SkIRect prevRect = prevFrame->frameRect();
if (!zero_rect(info, pixels, rowBytes, this->dimensions(), prevRect)) {
return kInternalError;
}
}
break;
default:
break;
}
} else {
Options prevFrameOptions(options);
prevFrameOptions.fFrameIndex = requiredFrame;
prevFrameOptions.fZeroInitialized = kNo_ZeroInitialized;
const Result result = this->getPixels(info, pixels, rowBytes, &prevFrameOptions);
if (result != kSuccess) {
return result;
}
const auto* prevFrame = frameHolder->getFrame(requiredFrame);
const auto disposalMethod = prevFrame->getDisposalMethod();
if (disposalMethod == SkCodecAnimation::DisposalMethod::kRestoreBGColor) {
auto prevRect = prevFrame->frameRect();
if (!zero_rect(info, pixels, rowBytes, this->dimensions(), prevRect)) {
return kInternalError;
}
}
}
}
return this->initializeColorXform(info, frame->reportedAlpha(), !frame->hasAlpha())
? kSuccess : kInvalidConversion;
}
SkCodec::Result SkCodec::getPixels(const SkImageInfo& dstInfo, void* pixels, size_t rowBytes,
const Options* options) {
SkImageInfo info = dstInfo;
if (!info.colorSpace()) {
info = info.makeColorSpace(SkColorSpace::MakeSRGB());
}
if (kUnknown_SkColorType == info.colorType()) {
return kInvalidConversion;
}
if (nullptr == pixels) {
return kInvalidParameters;
}
if (rowBytes < info.minRowBytes()) {
return kInvalidParameters;
}
if (!this->rewindIfNeeded()) {
return kCouldNotRewind;
}
// Default options.
Options optsStorage;
if (nullptr == options) {
options = &optsStorage;
} else {
if (options->fSubset) {
SkIRect subset(*options->fSubset);
if (!this->onGetValidSubset(&subset) || subset != *options->fSubset) {
// FIXME: How to differentiate between not supporting subset at all
// and not supporting this particular subset?
return kUnimplemented;
}
}
}
const Result frameIndexResult = this->handleFrameIndex(info, pixels, rowBytes,
*options);
if (frameIndexResult != kSuccess) {
return frameIndexResult;
}
// FIXME: Support subsets somehow? Note that this works for SkWebpCodec
// because it supports arbitrary scaling/subset combinations.
if (!this->dimensionsSupported(info.dimensions())) {
return kInvalidScale;
}
fDstInfo = info;
fOptions = *options;
// On an incomplete decode, the subclass will specify the number of scanlines that it decoded
// successfully.
int rowsDecoded = 0;
const Result result = this->onGetPixels(info, pixels, rowBytes, *options, &rowsDecoded);
// A return value of kIncompleteInput indicates a truncated image stream.
// In this case, we will fill any uninitialized memory with a default value.
// Some subclasses will take care of filling any uninitialized memory on
// their own. They indicate that all of the memory has been filled by
// setting rowsDecoded equal to the height.
if ((kIncompleteInput == result || kErrorInInput == result) && rowsDecoded != info.height()) {
// FIXME: (skbug.com/5772) fillIncompleteImage will fill using the swizzler's width, unless
// there is a subset. In that case, it will use the width of the subset. From here, the
// subset will only be non-null in the case of SkWebpCodec, but it treats the subset
// differenty from the other codecs, and it needs to use the width specified by the info.
// Set the subset to null so SkWebpCodec uses the correct width.
fOptions.fSubset = nullptr;
this->fillIncompleteImage(info, pixels, rowBytes, options->fZeroInitialized, info.height(),
rowsDecoded);
}
return result;
}
SkCodec::Result SkCodec::startIncrementalDecode(const SkImageInfo& dstInfo, void* pixels,
size_t rowBytes, const SkCodec::Options* options) {
fStartedIncrementalDecode = false;
SkImageInfo info = dstInfo;
if (!info.colorSpace()) {
info = info.makeColorSpace(SkColorSpace::MakeSRGB());
}
if (kUnknown_SkColorType == info.colorType()) {
return kInvalidConversion;
}
if (nullptr == pixels) {
return kInvalidParameters;
}
// FIXME: If the rows come after the rows of a previous incremental decode,
// we might be able to skip the rewind, but only the implementation knows
// that. (e.g. PNG will always need to rewind, since we called longjmp, but
// a bottom-up BMP could skip rewinding if the new rows are above the old
// rows.)
if (!this->rewindIfNeeded()) {
return kCouldNotRewind;
}
// Set options.
Options optsStorage;
if (nullptr == options) {
options = &optsStorage;
} else {
if (options->fSubset) {
SkIRect size = SkIRect::MakeSize(info.dimensions());
if (!size.contains(*options->fSubset)) {
return kInvalidParameters;
}
const int top = options->fSubset->top();
const int bottom = options->fSubset->bottom();
if (top < 0 || top >= info.height() || top >= bottom || bottom > info.height()) {
return kInvalidParameters;
}
}
}
const Result frameIndexResult = this->handleFrameIndex(info, pixels, rowBytes,
*options);
if (frameIndexResult != kSuccess) {
return frameIndexResult;
}
if (!this->dimensionsSupported(info.dimensions())) {
return kInvalidScale;
}
fDstInfo = info;
fOptions = *options;
const Result result = this->onStartIncrementalDecode(info, pixels, rowBytes, fOptions);
if (kSuccess == result) {
fStartedIncrementalDecode = true;
} else if (kUnimplemented == result) {
// FIXME: This is temporarily necessary, until we transition SkCodec
// implementations from scanline decoding to incremental decoding.
// SkAndroidCodec will first attempt to use incremental decoding, but
// will fall back to scanline decoding if incremental returns
// kUnimplemented. rewindIfNeeded(), above, set fNeedsRewind to true
// (after potentially rewinding), but we do not want the next call to
// startScanlineDecode() to do a rewind.
fNeedsRewind = false;
}
return result;
}
SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo,
const SkCodec::Options* options) {
// Reset fCurrScanline in case of failure.
fCurrScanline = -1;
SkImageInfo info = dstInfo;
if (!info.colorSpace()) {
info = info.makeColorSpace(SkColorSpace::MakeSRGB());
}
if (!this->rewindIfNeeded()) {
return kCouldNotRewind;
}
// Set options.
Options optsStorage;
if (nullptr == options) {
options = &optsStorage;
} else if (options->fSubset) {
SkIRect size = SkIRect::MakeSize(info.dimensions());
if (!size.contains(*options->fSubset)) {
return kInvalidInput;
}
// We only support subsetting in the x-dimension for scanline decoder.
// Subsetting in the y-dimension can be accomplished using skipScanlines().
if (options->fSubset->top() != 0 || options->fSubset->height() != info.height()) {
return kInvalidInput;
}
}
// Scanline decoding only supports decoding the first frame.
if (options->fFrameIndex != 0) {
return kUnimplemented;
}
// The void* dst and rowbytes in handleFrameIndex or only used for decoding prior
// frames, which is not supported here anyway, so it is safe to pass nullptr/0.
const Result frameIndexResult = this->handleFrameIndex(info, nullptr, 0, *options);
if (frameIndexResult != kSuccess) {
return frameIndexResult;
}
// FIXME: Support subsets somehow?
if (!this->dimensionsSupported(info.dimensions())) {
return kInvalidScale;
}
const Result result = this->onStartScanlineDecode(info, *options);
if (result != SkCodec::kSuccess) {
return result;
}
fCurrScanline = 0;
fDstInfo = info;
fOptions = *options;
return kSuccess;
}
int SkCodec::getScanlines(void* dst, int countLines, size_t rowBytes) {
if (fCurrScanline < 0) {
return 0;
}
SkASSERT(!fDstInfo.isEmpty());
if (countLines <= 0 || fCurrScanline + countLines > fDstInfo.height()) {
return 0;
}
const int linesDecoded = this->onGetScanlines(dst, countLines, rowBytes);
if (linesDecoded < countLines) {
this->fillIncompleteImage(this->dstInfo(), dst, rowBytes, this->options().fZeroInitialized,
countLines, linesDecoded);
}
fCurrScanline += countLines;
return linesDecoded;
}
bool SkCodec::skipScanlines(int countLines) {
if (fCurrScanline < 0) {
return false;
}
SkASSERT(!fDstInfo.isEmpty());
if (countLines < 0 || fCurrScanline + countLines > fDstInfo.height()) {
// Arguably, we could just skip the scanlines which are remaining,
// and return true. We choose to return false so the client
// can catch their bug.
return false;
}
bool result = this->onSkipScanlines(countLines);
fCurrScanline += countLines;
return result;
}
int SkCodec::outputScanline(int inputScanline) const {
SkASSERT(0 <= inputScanline && inputScanline < fEncodedInfo.height());
return this->onOutputScanline(inputScanline);
}
int SkCodec::onOutputScanline(int inputScanline) const {
switch (this->getScanlineOrder()) {
case kTopDown_SkScanlineOrder:
return inputScanline;
case kBottomUp_SkScanlineOrder:
return fEncodedInfo.height() - inputScanline - 1;
default:
// This case indicates an interlaced gif and is implemented by SkGifCodec.
SkASSERT(false);
return 0;
}
}
void SkCodec::fillIncompleteImage(const SkImageInfo& info, void* dst, size_t rowBytes,
ZeroInitialized zeroInit, int linesRequested, int linesDecoded) {
if (kYes_ZeroInitialized == zeroInit) {
return;
}
const int linesRemaining = linesRequested - linesDecoded;
SkSampler* sampler = this->getSampler(false);
const int fillWidth = sampler ? sampler->fillWidth() :
fOptions.fSubset ? fOptions.fSubset->width() :
info.width() ;
void* fillDst = this->getScanlineOrder() == kBottomUp_SkScanlineOrder ? dst :
SkTAddOffset<void>(dst, linesDecoded * rowBytes);
const auto fillInfo = info.makeWH(fillWidth, linesRemaining);
SkSampler::Fill(fillInfo, fillDst, rowBytes, kNo_ZeroInitialized);
}
bool sk_select_xform_format(SkColorType colorType, bool forColorTable,
skcms_PixelFormat* outFormat) {
SkASSERT(outFormat);
switch (colorType) {
case kRGBA_8888_SkColorType:
*outFormat = skcms_PixelFormat_RGBA_8888;
break;
case kBGRA_8888_SkColorType:
*outFormat = skcms_PixelFormat_BGRA_8888;
break;
case kRGB_565_SkColorType:
if (forColorTable) {
#if defined(STARBOARD)
*outFormat = (GetSkPmcolor() == SkPmcolorIsRgba) ? skcms_PixelFormat_RGBA_8888
: skcms_PixelFormat_RGBA_8888;
#else
#ifdef SK_PMCOLOR_IS_RGBA
*outFormat = skcms_PixelFormat_RGBA_8888;
#else
*outFormat = skcms_PixelFormat_BGRA_8888;
#endif
#endif
break;
}
*outFormat = skcms_PixelFormat_BGR_565;
break;
case kRGBA_F16_SkColorType:
*outFormat = skcms_PixelFormat_RGBA_hhhh;
break;
case kGray_8_SkColorType:
*outFormat = skcms_PixelFormat_G_8;
break;
default:
return false;
}
return true;
}
bool SkCodec::initializeColorXform(const SkImageInfo& dstInfo, SkEncodedInfo::Alpha encodedAlpha,
bool srcIsOpaque) {
fXformTime = kNo_XformTime;
bool needsColorXform = false;
if (this->usesColorXform() && dstInfo.colorSpace()) {
dstInfo.colorSpace()->toProfile(&fDstProfile);
if (kRGBA_F16_SkColorType == dstInfo.colorType()) {
needsColorXform = true;
} else {
const auto* srcProfile = fEncodedInfo.profile();
if (!srcProfile) {
srcProfile = skcms_sRGB_profile();
}
if (!skcms_ApproximatelyEqualProfiles(srcProfile, &fDstProfile) ) {
needsColorXform = true;
}
}
}
if (!this->conversionSupported(dstInfo, srcIsOpaque, needsColorXform)) {
return false;
}
if (needsColorXform) {
fXformTime = SkEncodedInfo::kPalette_Color != fEncodedInfo.color()
|| kRGBA_F16_SkColorType == dstInfo.colorType()
? kDecodeRow_XformTime : kPalette_XformTime;
if (!sk_select_xform_format(dstInfo.colorType(), fXformTime == kPalette_XformTime,
&fDstXformFormat)) {
return false;
}
if (encodedAlpha == SkEncodedInfo::kUnpremul_Alpha
&& dstInfo.alphaType() == kPremul_SkAlphaType) {
fDstXformAlphaFormat = skcms_AlphaFormat_PremulAsEncoded;
} else {
fDstXformAlphaFormat = skcms_AlphaFormat_Unpremul;
}
}
return true;
}
void SkCodec::applyColorXform(void* dst, const void* src, int count) const {
// It is okay for srcProfile to be null. This will use sRGB.
const auto* srcProfile = fEncodedInfo.profile();
SkAssertResult(skcms_Transform(src, fSrcXformFormat, skcms_AlphaFormat_Unpremul, srcProfile,
dst, fDstXformFormat, fDstXformAlphaFormat, &fDstProfile,
count));
}
std::vector<SkCodec::FrameInfo> SkCodec::getFrameInfo() {
const int frameCount = this->getFrameCount();
SkASSERT(frameCount >= 0);
if (frameCount <= 0) {
return std::vector<FrameInfo>{};
}
if (frameCount == 1 && !this->onGetFrameInfo(0, nullptr)) {
// Not animated.
return std::vector<FrameInfo>{};
}
std::vector<FrameInfo> result(frameCount);
for (int i = 0; i < frameCount; ++i) {
SkAssertResult(this->onGetFrameInfo(i, &result[i]));
}
return result;
}
const char* SkCodec::ResultToString(Result result) {
switch (result) {
case kSuccess:
return "success";
case kIncompleteInput:
return "incomplete input";
case kErrorInInput:
return "error in input";
case kInvalidConversion:
return "invalid conversion";
case kInvalidScale:
return "invalid scale";
case kInvalidParameters:
return "invalid parameters";
case kInvalidInput:
return "invalid input";
case kCouldNotRewind:
return "could not rewind";
case kInternalError:
return "internal error";
case kUnimplemented:
return "unimplemented";
default:
SkASSERT(false);
return "bogus result value";
}
}
static bool independent(const SkFrame& frame) {
return frame.getRequiredFrame() == SkCodec::kNoFrame;
}
static bool restore_bg(const SkFrame& frame) {
return frame.getDisposalMethod() == SkCodecAnimation::DisposalMethod::kRestoreBGColor;
}
// As its name suggests, this method computes a frame's alpha (e.g. completely
// opaque, unpremul, binary) and its required frame (a preceding frame that
// this frame depends on, to draw the complete image at this frame's point in
// the animation stream), and calls this frame's setter methods with that
// computed information.
//
// A required frame of kNoFrame means that this frame is independent: drawing
// the complete image at this frame's point in the animation stream does not
// require first preparing the pixel buffer based on another frame. Instead,
// drawing can start from an uninitialized pixel buffer.
//
// "Uninitialized" is from the SkCodec's caller's point of view. In the SkCodec
// implementation, for independent frames, first party Skia code (in src/codec)
// will typically fill the buffer with a uniform background color (e.g.
// transparent black) before calling into third party codec-specific code (e.g.
// libjpeg or libpng). Pixels outside of the frame's rect will remain this
// background color after drawing this frame. For incomplete decodes, pixels
// inside that rect may be (at least temporarily) set to that background color.
// In an incremental decode, later passes may then overwrite that background
// color.
//
// Determining kNoFrame or otherwise involves testing a number of conditions
// sequentially. The first satisfied condition results in setting the required
// frame to kNoFrame (an "INDx" condition) or to a non-negative frame number (a
// "DEPx" condition), and the function returning early. Those "INDx" and "DEPx"
// labels also map to comments in the function body.
//
// - IND1: this frame is the first frame.
// - IND2: this frame fills out the whole image, and it is completely opaque
// or it overwrites (not blends with) the previous frame.
// - IND3: all preceding frames' disposals are kRestorePrevious.
// - IND4: the prevFrame's disposal is kRestoreBGColor, and it fills out the
// whole image or it is itself otherwise independent.
// - DEP5: this frame reports alpha (it is not completely opaque) and it
// blends with (not overwrites) the previous frame.
// - IND6: this frame's rect covers the rects of all preceding frames back to
// and including the most recent independent frame before this frame.
// - DEP7: unconditional.
//
// The "prevFrame" variable initially points to the previous frame (also known
// as the prior frame), but that variable may iterate further backwards over
// the course of this computation.
void SkFrameHolder::setAlphaAndRequiredFrame(SkFrame* frame) {
const bool reportsAlpha = frame->reportedAlpha() != SkEncodedInfo::kOpaque_Alpha;
const auto screenRect = SkIRect::MakeWH(fScreenWidth, fScreenHeight);
const auto frameRect = frame_rect_on_screen(frame->frameRect(), screenRect);
const int i = frame->frameId();
if (0 == i) {
frame->setHasAlpha(reportsAlpha || frameRect != screenRect);
frame->setRequiredFrame(SkCodec::kNoFrame); // IND1
return;
}
const bool blendWithPrevFrame = frame->getBlend() == SkCodecAnimation::Blend::kPriorFrame;
if ((!reportsAlpha || !blendWithPrevFrame) && frameRect == screenRect) {
frame->setHasAlpha(reportsAlpha);
frame->setRequiredFrame(SkCodec::kNoFrame); // IND2
return;
}
const SkFrame* prevFrame = this->getFrame(i-1);
while (prevFrame->getDisposalMethod() == SkCodecAnimation::DisposalMethod::kRestorePrevious) {
const int prevId = prevFrame->frameId();
if (0 == prevId) {
frame->setHasAlpha(true);
frame->setRequiredFrame(SkCodec::kNoFrame); // IND3
return;
}
prevFrame = this->getFrame(prevId - 1);
}
const bool clearPrevFrame = restore_bg(*prevFrame);
auto prevFrameRect = frame_rect_on_screen(prevFrame->frameRect(), screenRect);
if (clearPrevFrame) {
if (prevFrameRect == screenRect || independent(*prevFrame)) {
frame->setHasAlpha(true);
frame->setRequiredFrame(SkCodec::kNoFrame); // IND4
return;
}
}
if (reportsAlpha && blendWithPrevFrame) {
// Note: We could be more aggressive here. If prevFrame clears
// to background color and covers its required frame (and that
// frame is independent), prevFrame could be marked independent.
// Would this extra complexity be worth it?
frame->setRequiredFrame(prevFrame->frameId()); // DEP5
frame->setHasAlpha(prevFrame->hasAlpha() || clearPrevFrame);
return;
}
while (frameRect.contains(prevFrameRect)) {
const int prevRequiredFrame = prevFrame->getRequiredFrame();
if (prevRequiredFrame == SkCodec::kNoFrame) {
frame->setRequiredFrame(SkCodec::kNoFrame); // IND6
frame->setHasAlpha(true);
return;
}
prevFrame = this->getFrame(prevRequiredFrame);
prevFrameRect = frame_rect_on_screen(prevFrame->frameRect(), screenRect);
}
frame->setRequiredFrame(prevFrame->frameId()); // DEP7
if (restore_bg(*prevFrame)) {
frame->setHasAlpha(true);
return;
}
SkASSERT(prevFrame->getDisposalMethod() == SkCodecAnimation::DisposalMethod::kKeep);
frame->setHasAlpha(prevFrame->hasAlpha() || (reportsAlpha && !blendWithPrevFrame));
}