src/codec/SkWebpCodec.cpp - platform/external/skia - Gitiles

 /*
  * 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 "SkCodecPriv.h"
 #include "SkColorSpaceXform.h"
 #include "SkSampler.h"
 #include "SkStreamPriv.h"
 #include "SkTemplates.h"
 #include "SkWebpCodec.h"

 // A WebP decoder on top of (subset of) libwebp
 // For more information on WebP image format, and libwebp library, see:
 //   https://code.google.com/speed/webp/
 //   http://www.webmproject.org/code/#libwebp-webp-image-library
 //   https://chromium.googlesource.com/webm/libwebp

 // If moving libwebp out of skia source tree, path for webp headers must be
 // updated accordingly. Here, we enforce using local copy in webp sub-directory.
 #include "webp/decode.h"
 #include "webp/demux.h"
 #include "webp/encode.h"

 bool SkWebpCodec::IsWebp(const void* buf, size_t bytesRead) {
     // WEBP starts with the following:
     // RIFFXXXXWEBPVP
     // Where XXXX is unspecified.
     const char* bytes = static_cast<const char*>(buf);
     return bytesRead >= 14 && !memcmp(bytes, "RIFF", 4) && !memcmp(&bytes[8], "WEBPVP", 6);
 }

 // Parse headers of RIFF container, and check for valid Webp (VP8) content.
 // NOTE: This calls peek instead of read, since onGetPixels will need these
 // bytes again.
 // Returns an SkWebpCodec on success;
 SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
     std::unique_ptr<SkStream> streamDeleter(stream);

     // Webp demux needs a contiguous data buffer.
     sk_sp<SkData> data = nullptr;
     if (stream->getMemoryBase()) {
         // It is safe to make without copy because we'll hold onto the stream.
         data = SkData::MakeWithoutCopy(stream->getMemoryBase(), stream->getLength());
     } else {
         data = SkCopyStreamToData(stream);

         // If we are forced to copy the stream to a data, we can go ahead and delete the stream.
         streamDeleter.reset(nullptr);
     }

     // It's a little strange that the |demux| will outlive |webpData|, though it needs the
     // pointer in |webpData| to remain valid.  This works because the pointer remains valid
     // until the SkData is freed.
     WebPData webpData = { data->bytes(), data->size() };
     SkAutoTCallVProc<WebPDemuxer, WebPDemuxDelete> demux(WebPDemuxPartial(&webpData, nullptr));
     if (nullptr == demux) {
         return nullptr;
     }

     const int width = WebPDemuxGetI(demux, WEBP_FF_CANVAS_WIDTH);
     const int height = WebPDemuxGetI(demux, WEBP_FF_CANVAS_HEIGHT);

     // Sanity check for image size that's about to be decoded.
     {
         const int64_t size = sk_64_mul(width, height);
         if (!sk_64_isS32(size)) {
             return nullptr;
         }
         // now check that if we are 4-bytes per pixel, we also don't overflow
         if (sk_64_asS32(size) > (0x7FFFFFFF >> 2)) {
             return nullptr;
         }
     }

     WebPChunkIterator chunkIterator;
     SkAutoTCallVProc<WebPChunkIterator, WebPDemuxReleaseChunkIterator> autoCI(&chunkIterator);
     sk_sp<SkColorSpace> colorSpace = nullptr;
     bool unsupportedICC = false;
     if (WebPDemuxGetChunk(demux, "ICCP", 1, &chunkIterator)) {
         colorSpace = SkColorSpace::MakeICC(chunkIterator.chunk.bytes, chunkIterator.chunk.size);
         if (!colorSpace) {
             unsupportedICC = true;
         }
     }
     if (!colorSpace) {
         colorSpace = SkColorSpace::MakeSRGB();
     }

     // Get the first frame and its "features" to determine the color and alpha types.
     // Since we do not yet support animated webp, this is the only frame that we will
     // decode.
     WebPIterator frame;
     SkAutoTCallVProc<WebPIterator, WebPDemuxReleaseIterator> autoFrame(&frame);
     if (!WebPDemuxGetFrame(demux, 1, &frame)) {
         return nullptr;
     }

     WebPBitstreamFeatures features;
     VP8StatusCode status = WebPGetFeatures(frame.fragment.bytes, frame.fragment.size, &features);
     if (VP8_STATUS_OK != status) {
         return nullptr;
     }

     SkEncodedInfo::Color color;
     SkEncodedInfo::Alpha alpha;
     switch (features.format) {
         case 0:
             // This indicates a "mixed" format.  We could see this for
             // animated webps (multiple fragments).
             // I believe that this is a rare case.
             // We could also guess kYUV here, but I think it makes more
             // sense to guess kBGRA which is likely closer to the final
             // output.  Otherwise, we might end up converting
             // BGRA->YUVA->BGRA.
             color = SkEncodedInfo::kBGRA_Color;
             alpha = SkEncodedInfo::kUnpremul_Alpha;
             break;
         case 1:
             // This is the lossy format (YUV).
             if (SkToBool(features.has_alpha) || frame.width != width || frame.height != height) {
                 color = SkEncodedInfo::kYUVA_Color;
                 alpha = SkEncodedInfo::kUnpremul_Alpha;
             } else {
                 color = SkEncodedInfo::kYUV_Color;
                 alpha = SkEncodedInfo::kOpaque_Alpha;
             }
             break;
         case 2:
             // This is the lossless format (BGRA).
             color = SkEncodedInfo::kBGRA_Color;
             alpha = SkEncodedInfo::kUnpremul_Alpha;
             break;
         default:
             return nullptr;
     }

     SkEncodedInfo info = SkEncodedInfo::Make(color, alpha, 8);
     SkWebpCodec* codecOut = new SkWebpCodec(width, height, info, std::move(colorSpace),
                                             streamDeleter.release(), demux.release(),
                                             std::move(data));
     codecOut->setUnsupportedICC(unsupportedICC);
     return codecOut;
 }

 SkISize SkWebpCodec::onGetScaledDimensions(float desiredScale) const {
     SkISize dim = this->getInfo().dimensions();
     // SkCodec treats zero dimensional images as errors, so the minimum size
     // that we will recommend is 1x1.
     dim.fWidth = SkTMax(1, SkScalarRoundToInt(desiredScale * dim.fWidth));
     dim.fHeight = SkTMax(1, SkScalarRoundToInt(desiredScale * dim.fHeight));
     return dim;
 }

 bool SkWebpCodec::onDimensionsSupported(const SkISize& dim) {
     const SkImageInfo& info = this->getInfo();
     return dim.width() >= 1 && dim.width() <= info.width()
             && dim.height() >= 1 && dim.height() <= info.height();
 }

 static WEBP_CSP_MODE webp_decode_mode(SkColorType ct, bool premultiply) {
     switch (ct) {
         case kBGRA_8888_SkColorType:
             return premultiply ? MODE_bgrA : MODE_BGRA;
         case kRGBA_8888_SkColorType:
             return premultiply ? MODE_rgbA : MODE_RGBA;
         case kRGB_565_SkColorType:
             return MODE_RGB_565;
         default:
             return MODE_LAST;
     }
 }

 bool SkWebpCodec::onGetValidSubset(SkIRect* desiredSubset) const {
     if (!desiredSubset) {
         return false;
     }

     SkIRect dimensions  = SkIRect::MakeSize(this->getInfo().dimensions());
     if (!dimensions.contains(*desiredSubset)) {
         return false;
     }

     // As stated below, libwebp snaps to even left and top. Make sure top and left are even, so we
     // decode this exact subset.
     // Leave right and bottom unmodified, so we suggest a slightly larger subset than requested.
     desiredSubset->fLeft = (desiredSubset->fLeft >> 1) << 1;
     desiredSubset->fTop = (desiredSubset->fTop >> 1) << 1;
     return true;
 }

 SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
                                          const Options& options, SkPMColor*, int*,
                                          int* rowsDecodedPtr) {
     if (!conversion_possible(dstInfo, this->getInfo()) ||
         !this->initializeColorXform(dstInfo, options.fPremulBehavior))
     {
         return kInvalidConversion;
     }

     WebPDecoderConfig config;
     if (0 == WebPInitDecoderConfig(&config)) {
         // ABI mismatch.
         // FIXME: New enum for this?
         return kInvalidInput;
     }

     // Free any memory associated with the buffer. Must be called last, so we declare it first.
     SkAutoTCallVProc<WebPDecBuffer, WebPFreeDecBuffer> autoFree(&(config.output));

     WebPIterator frame;
     SkAutoTCallVProc<WebPIterator, WebPDemuxReleaseIterator> autoFrame(&frame);
     // If this succeeded in NewFromStream(), it should succeed again here.
     SkAssertResult(WebPDemuxGetFrame(fDemux, 1, &frame));

     // Get the frameRect.  libwebp will have already signaled an error if this is not fully
     // contained by the canvas.
     auto frameRect = SkIRect::MakeXYWH(frame.x_offset, frame.y_offset, frame.width, frame.height);
     SkASSERT(this->getInfo().bounds().contains(frameRect));
     bool frameIsSubset = frameRect.size() != this->getInfo().dimensions();
     if (frameIsSubset) {
         SkSampler::Fill(dstInfo, dst, rowBytes, 0, options.fZeroInitialized);
     }

     int dstX = frameRect.x();
     int dstY = frameRect.y();
     int subsetWidth = frameRect.width();
     int subsetHeight = frameRect.height();
     if (options.fSubset) {
         SkIRect subset = *options.fSubset;
         SkASSERT(this->getInfo().bounds().contains(subset));
         SkASSERT(SkIsAlign2(subset.fLeft) && SkIsAlign2(subset.fTop));
         SkASSERT(this->getValidSubset(&subset) && subset == *options.fSubset);

         if (!SkIRect::IntersectsNoEmptyCheck(subset, frameRect)) {
             return kSuccess;
         }

         int minXOffset = SkTMin(dstX, subset.x());
         int minYOffset = SkTMin(dstY, subset.y());
         dstX -= minXOffset;
         dstY -= minYOffset;
         frameRect.offset(-minXOffset, -minYOffset);
         subset.offset(-minXOffset, -minYOffset);

         // Just like we require that the requested subset x and y offset are even, libwebp
         // guarantees that the frame x and y offset are even (it's actually impossible to specify
         // an odd frame offset).  So we can still guarantee that the adjusted offsets are even.
         SkASSERT(SkIsAlign2(subset.fLeft) && SkIsAlign2(subset.fTop));

         SkIRect intersection;
         SkAssertResult(intersection.intersect(frameRect, subset));
         subsetWidth = intersection.width();
         subsetHeight = intersection.height();

         config.options.use_cropping = 1;
         config.options.crop_left = subset.x();
         config.options.crop_top = subset.y();
         config.options.crop_width = subsetWidth;
         config.options.crop_height = subsetHeight;
     }

     // Ignore the frame size and offset when determining if scaling is necessary.
     int scaledWidth = subsetWidth;
     int scaledHeight = subsetHeight;
     SkISize srcSize = options.fSubset ? options.fSubset->size() : this->getInfo().dimensions();
     if (srcSize != dstInfo.dimensions()) {
         config.options.use_scaling = 1;

         if (frameIsSubset) {
             float scaleX = ((float) dstInfo.width()) / srcSize.width();
             float scaleY = ((float) dstInfo.height()) / srcSize.height();

             // We need to be conservative here and floor rather than round.
             // Otherwise, we may find ourselves decoding off the end of memory.
             dstX = scaleX * dstX;
             scaledWidth = scaleX * scaledWidth;
             dstY = scaleY * dstY;
             scaledHeight = scaleY * scaledHeight;
             if (0 == scaledWidth || 0 == scaledHeight) {
                 return kSuccess;
             }
         } else {
             scaledWidth = dstInfo.width();
             scaledHeight = dstInfo.height();
         }

         config.options.scaled_width = scaledWidth;
         config.options.scaled_height = scaledHeight;
     }

     // Swizzling between RGBA and BGRA is zero cost in a color transform.  So when we have a
     // color transform, we should decode to whatever is easiest for libwebp, and then let the
     // color transform swizzle if necessary.
     // Lossy webp is encoded as YUV (so RGBA and BGRA are the same cost).  Lossless webp is
     // encoded as BGRA. This means decoding to BGRA is either faster or the same cost as RGBA.
     config.output.colorspace = this->colorXform() ? MODE_BGRA :
             webp_decode_mode(dstInfo.colorType(), dstInfo.alphaType() == kPremul_SkAlphaType);
     config.output.is_external_memory = 1;

     // We will decode the entire image and then perform the color transform.  libwebp
     // does not provide a row-by-row API.  This is a shame particularly when we do not want
     // 8888, since we will need to create another image sized buffer.
     SkAutoTMalloc<uint32_t> pixels;
     bool needsCopy = this->colorXform() && kRGBA_8888_SkColorType != dstInfo.colorType() &&
                                            kBGRA_8888_SkColorType != dstInfo.colorType();
     void* webpDst = needsCopy ? pixels.reset(dstInfo.width() * dstInfo.height()) : dst;
     size_t webpRowBytes = needsCopy ? dstInfo.width() * sizeof(uint32_t) : rowBytes;
     size_t totalBytes = needsCopy ? webpRowBytes * dstInfo.height()
                                   : dstInfo.getSafeSize(webpRowBytes);
     size_t dstBpp = SkColorTypeBytesPerPixel(dstInfo.colorType());
     size_t webpBpp = needsCopy ? sizeof(uint32_t) : dstBpp;

     size_t offset = dstX * webpBpp + dstY * webpRowBytes;
     config.output.u.RGBA.rgba = SkTAddOffset<uint8_t>(webpDst, offset);
     config.output.u.RGBA.stride = (int) webpRowBytes;
     config.output.u.RGBA.size = totalBytes - offset;

     SkAutoTCallVProc<WebPIDecoder, WebPIDelete> idec(WebPIDecode(nullptr, 0, &config));
     if (!idec) {
         return kInvalidInput;
     }

     int rowsDecoded;
     SkCodec::Result result;
     switch (WebPIUpdate(idec, frame.fragment.bytes, frame.fragment.size)) {
         case VP8_STATUS_OK:
             rowsDecoded = scaledHeight;
             result = kSuccess;
             break;
         case VP8_STATUS_SUSPENDED:
             WebPIDecGetRGB(idec, &rowsDecoded, nullptr, nullptr, nullptr);
             *rowsDecodedPtr = rowsDecoded + dstY;
             result = kIncompleteInput;
             break;
         default:
             return kInvalidInput;
     }

     if (this->colorXform()) {
         SkColorSpaceXform::ColorFormat dstColorFormat = select_xform_format(dstInfo.colorType());
         SkAlphaType xformAlphaType = select_xform_alpha(dstInfo.alphaType(),
                                                         this->getInfo().alphaType());

         uint32_t* xformSrc = (uint32_t*) config.output.u.RGBA.rgba;
         void* xformDst = SkTAddOffset<void>(dst, dstBpp * dstX + rowBytes * dstY);
         size_t srcRowBytes = config.output.u.RGBA.stride;
         for (int y = 0; y < rowsDecoded; y++) {
             SkAssertResult(this->colorXform()->apply(dstColorFormat, xformDst,
                     SkColorSpaceXform::kBGRA_8888_ColorFormat, xformSrc, scaledWidth,
                     xformAlphaType));
             xformDst = SkTAddOffset<void>(xformDst, rowBytes);
             xformSrc = SkTAddOffset<uint32_t>(xformSrc, srcRowBytes);
         }
     }

     return result;
 }

 SkWebpCodec::SkWebpCodec(int width, int height, const SkEncodedInfo& info,
                          sk_sp<SkColorSpace> colorSpace, SkStream* stream, WebPDemuxer* demux,
                          sk_sp<SkData> data)
     : INHERITED(width, height, info, stream, std::move(colorSpace))
     , fDemux(demux)
     , fData(std::move(data))
 {}
	/*
	* 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 "SkCodecPriv.h"
	#include "SkColorSpaceXform.h"
	#include "SkSampler.h"
	#include "SkStreamPriv.h"
	#include "SkTemplates.h"
	#include "SkWebpCodec.h"

	// A WebP decoder on top of (subset of) libwebp
	// For more information on WebP image format, and libwebp library, see:
	// https://code.google.com/speed/webp/
	// http://www.webmproject.org/code/#libwebp-webp-image-library
	// https://chromium.googlesource.com/webm/libwebp

	// If moving libwebp out of skia source tree, path for webp headers must be
	// updated accordingly. Here, we enforce using local copy in webp sub-directory.
	#include "webp/decode.h"
	#include "webp/demux.h"
	#include "webp/encode.h"

	bool SkWebpCodec::IsWebp(const void* buf, size_t bytesRead) {
	// WEBP starts with the following:
	// RIFFXXXXWEBPVP
	// Where XXXX is unspecified.
	const char* bytes = static_cast<const char*>(buf);
	return bytesRead >= 14 && !memcmp(bytes, "RIFF", 4) && !memcmp(&bytes[8], "WEBPVP", 6);
	}

	// Parse headers of RIFF container, and check for valid Webp (VP8) content.
	// NOTE: This calls peek instead of read, since onGetPixels will need these
	// bytes again.
	// Returns an SkWebpCodec on success;
	SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
	std::unique_ptr<SkStream> streamDeleter(stream);

	// Webp demux needs a contiguous data buffer.
	sk_sp<SkData> data = nullptr;
	if (stream->getMemoryBase()) {
	// It is safe to make without copy because we'll hold onto the stream.
	data = SkData::MakeWithoutCopy(stream->getMemoryBase(), stream->getLength());
	} else {
	data = SkCopyStreamToData(stream);

	// If we are forced to copy the stream to a data, we can go ahead and delete the stream.
	streamDeleter.reset(nullptr);
	}

	// It's a little strange that the \|demux\| will outlive \|webpData\|, though it needs the
	// pointer in \|webpData\| to remain valid. This works because the pointer remains valid
	// until the SkData is freed.
	WebPData webpData = { data->bytes(), data->size() };
	SkAutoTCallVProc<WebPDemuxer, WebPDemuxDelete> demux(WebPDemuxPartial(&webpData, nullptr));
	if (nullptr == demux) {
	return nullptr;
	}

	const int width = WebPDemuxGetI(demux, WEBP_FF_CANVAS_WIDTH);
	const int height = WebPDemuxGetI(demux, WEBP_FF_CANVAS_HEIGHT);

	// Sanity check for image size that's about to be decoded.
	{
	const int64_t size = sk_64_mul(width, height);
	if (!sk_64_isS32(size)) {
	return nullptr;
	}
	// now check that if we are 4-bytes per pixel, we also don't overflow
	if (sk_64_asS32(size) > (0x7FFFFFFF >> 2)) {
	return nullptr;
	}
	}

	WebPChunkIterator chunkIterator;
	SkAutoTCallVProc<WebPChunkIterator, WebPDemuxReleaseChunkIterator> autoCI(&chunkIterator);
	sk_sp<SkColorSpace> colorSpace = nullptr;
	bool unsupportedICC = false;
	if (WebPDemuxGetChunk(demux, "ICCP", 1, &chunkIterator)) {
	colorSpace = SkColorSpace::MakeICC(chunkIterator.chunk.bytes, chunkIterator.chunk.size);
	if (!colorSpace) {
	unsupportedICC = true;
	}
	}
	if (!colorSpace) {
	colorSpace = SkColorSpace::MakeSRGB();
	}

	// Get the first frame and its "features" to determine the color and alpha types.
	// Since we do not yet support animated webp, this is the only frame that we will
	// decode.
	WebPIterator frame;
	SkAutoTCallVProc<WebPIterator, WebPDemuxReleaseIterator> autoFrame(&frame);
	if (!WebPDemuxGetFrame(demux, 1, &frame)) {
	return nullptr;
	}

	WebPBitstreamFeatures features;
	VP8StatusCode status = WebPGetFeatures(frame.fragment.bytes, frame.fragment.size, &features);
	if (VP8_STATUS_OK != status) {
	return nullptr;
	}

	SkEncodedInfo::Color color;
	SkEncodedInfo::Alpha alpha;
	switch (features.format) {
	case 0:
	// This indicates a "mixed" format. We could see this for
	// animated webps (multiple fragments).
	// I believe that this is a rare case.
	// We could also guess kYUV here, but I think it makes more
	// sense to guess kBGRA which is likely closer to the final
	// output. Otherwise, we might end up converting
	// BGRA->YUVA->BGRA.
	color = SkEncodedInfo::kBGRA_Color;
	alpha = SkEncodedInfo::kUnpremul_Alpha;
	break;
	case 1:
	// This is the lossy format (YUV).
	if (SkToBool(features.has_alpha) \|\| frame.width != width \|\| frame.height != height) {
	color = SkEncodedInfo::kYUVA_Color;
	alpha = SkEncodedInfo::kUnpremul_Alpha;
	} else {
	color = SkEncodedInfo::kYUV_Color;
	alpha = SkEncodedInfo::kOpaque_Alpha;
	}
	break;
	case 2:
	// This is the lossless format (BGRA).
	color = SkEncodedInfo::kBGRA_Color;
	alpha = SkEncodedInfo::kUnpremul_Alpha;
	break;
	default:
	return nullptr;
	}

	SkEncodedInfo info = SkEncodedInfo::Make(color, alpha, 8);
	SkWebpCodec* codecOut = new SkWebpCodec(width, height, info, std::move(colorSpace),
	streamDeleter.release(), demux.release(),
	std::move(data));
	codecOut->setUnsupportedICC(unsupportedICC);
	return codecOut;
	}

	SkISize SkWebpCodec::onGetScaledDimensions(float desiredScale) const {
	SkISize dim = this->getInfo().dimensions();
	// SkCodec treats zero dimensional images as errors, so the minimum size
	// that we will recommend is 1x1.
	dim.fWidth = SkTMax(1, SkScalarRoundToInt(desiredScale * dim.fWidth));
	dim.fHeight = SkTMax(1, SkScalarRoundToInt(desiredScale * dim.fHeight));
	return dim;
	}

	bool SkWebpCodec::onDimensionsSupported(const SkISize& dim) {
	const SkImageInfo& info = this->getInfo();
	return dim.width() >= 1 && dim.width() <= info.width()
	&& dim.height() >= 1 && dim.height() <= info.height();
	}

	static WEBP_CSP_MODE webp_decode_mode(SkColorType ct, bool premultiply) {
	switch (ct) {
	case kBGRA_8888_SkColorType:
	return premultiply ? MODE_bgrA : MODE_BGRA;
	case kRGBA_8888_SkColorType:
	return premultiply ? MODE_rgbA : MODE_RGBA;
	case kRGB_565_SkColorType:
	return MODE_RGB_565;
	default:
	return MODE_LAST;
	}
	}

	bool SkWebpCodec::onGetValidSubset(SkIRect* desiredSubset) const {
	if (!desiredSubset) {
	return false;
	}

	SkIRect dimensions = SkIRect::MakeSize(this->getInfo().dimensions());
	if (!dimensions.contains(*desiredSubset)) {
	return false;
	}

	// As stated below, libwebp snaps to even left and top. Make sure top and left are even, so we
	// decode this exact subset.
	// Leave right and bottom unmodified, so we suggest a slightly larger subset than requested.
	desiredSubset->fLeft = (desiredSubset->fLeft >> 1) << 1;
	desiredSubset->fTop = (desiredSubset->fTop >> 1) << 1;
	return true;
	}

	SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
	const Options& options, SkPMColor, int,
	int* rowsDecodedPtr) {
	if (!conversion_possible(dstInfo, this->getInfo()) \|\|
	!this->initializeColorXform(dstInfo, options.fPremulBehavior))
	{
	return kInvalidConversion;
	}

	WebPDecoderConfig config;
	if (0 == WebPInitDecoderConfig(&config)) {
	// ABI mismatch.
	// FIXME: New enum for this?
	return kInvalidInput;
	}

	// Free any memory associated with the buffer. Must be called last, so we declare it first.
	SkAutoTCallVProc<WebPDecBuffer, WebPFreeDecBuffer> autoFree(&(config.output));

	WebPIterator frame;
	SkAutoTCallVProc<WebPIterator, WebPDemuxReleaseIterator> autoFrame(&frame);
	// If this succeeded in NewFromStream(), it should succeed again here.
	SkAssertResult(WebPDemuxGetFrame(fDemux, 1, &frame));

	// Get the frameRect. libwebp will have already signaled an error if this is not fully
	// contained by the canvas.
	auto frameRect = SkIRect::MakeXYWH(frame.x_offset, frame.y_offset, frame.width, frame.height);
	SkASSERT(this->getInfo().bounds().contains(frameRect));
	bool frameIsSubset = frameRect.size() != this->getInfo().dimensions();
	if (frameIsSubset) {
	SkSampler::Fill(dstInfo, dst, rowBytes, 0, options.fZeroInitialized);
	}

	int dstX = frameRect.x();
	int dstY = frameRect.y();
	int subsetWidth = frameRect.width();
	int subsetHeight = frameRect.height();
	if (options.fSubset) {
	SkIRect subset = *options.fSubset;
	SkASSERT(this->getInfo().bounds().contains(subset));
	SkASSERT(SkIsAlign2(subset.fLeft) && SkIsAlign2(subset.fTop));
	SkASSERT(this->getValidSubset(&subset) && subset == *options.fSubset);

	if (!SkIRect::IntersectsNoEmptyCheck(subset, frameRect)) {
	return kSuccess;
	}

	int minXOffset = SkTMin(dstX, subset.x());
	int minYOffset = SkTMin(dstY, subset.y());
	dstX -= minXOffset;
	dstY -= minYOffset;
	frameRect.offset(-minXOffset, -minYOffset);
	subset.offset(-minXOffset, -minYOffset);

	// Just like we require that the requested subset x and y offset are even, libwebp
	// guarantees that the frame x and y offset are even (it's actually impossible to specify
	// an odd frame offset). So we can still guarantee that the adjusted offsets are even.
	SkASSERT(SkIsAlign2(subset.fLeft) && SkIsAlign2(subset.fTop));

	SkIRect intersection;
	SkAssertResult(intersection.intersect(frameRect, subset));
	subsetWidth = intersection.width();
	subsetHeight = intersection.height();

	config.options.use_cropping = 1;
	config.options.crop_left = subset.x();
	config.options.crop_top = subset.y();
	config.options.crop_width = subsetWidth;
	config.options.crop_height = subsetHeight;
	}

	// Ignore the frame size and offset when determining if scaling is necessary.
	int scaledWidth = subsetWidth;
	int scaledHeight = subsetHeight;
	SkISize srcSize = options.fSubset ? options.fSubset->size() : this->getInfo().dimensions();
	if (srcSize != dstInfo.dimensions()) {
	config.options.use_scaling = 1;

	if (frameIsSubset) {
	float scaleX = ((float) dstInfo.width()) / srcSize.width();
	float scaleY = ((float) dstInfo.height()) / srcSize.height();

	// We need to be conservative here and floor rather than round.
	// Otherwise, we may find ourselves decoding off the end of memory.
	dstX = scaleX * dstX;
	scaledWidth = scaleX * scaledWidth;
	dstY = scaleY * dstY;
	scaledHeight = scaleY * scaledHeight;
	if (0 == scaledWidth \|\| 0 == scaledHeight) {
	return kSuccess;
	}
	} else {
	scaledWidth = dstInfo.width();
	scaledHeight = dstInfo.height();
	}

	config.options.scaled_width = scaledWidth;
	config.options.scaled_height = scaledHeight;
	}

	// Swizzling between RGBA and BGRA is zero cost in a color transform. So when we have a
	// color transform, we should decode to whatever is easiest for libwebp, and then let the
	// color transform swizzle if necessary.
	// Lossy webp is encoded as YUV (so RGBA and BGRA are the same cost). Lossless webp is
	// encoded as BGRA. This means decoding to BGRA is either faster or the same cost as RGBA.
	config.output.colorspace = this->colorXform() ? MODE_BGRA :
	webp_decode_mode(dstInfo.colorType(), dstInfo.alphaType() == kPremul_SkAlphaType);
	config.output.is_external_memory = 1;

	// We will decode the entire image and then perform the color transform. libwebp
	// does not provide a row-by-row API. This is a shame particularly when we do not want
	// 8888, since we will need to create another image sized buffer.
	SkAutoTMalloc<uint32_t> pixels;
	bool needsCopy = this->colorXform() && kRGBA_8888_SkColorType != dstInfo.colorType() &&
	kBGRA_8888_SkColorType != dstInfo.colorType();
	void* webpDst = needsCopy ? pixels.reset(dstInfo.width() * dstInfo.height()) : dst;
	size_t webpRowBytes = needsCopy ? dstInfo.width() * sizeof(uint32_t) : rowBytes;
	size_t totalBytes = needsCopy ? webpRowBytes * dstInfo.height()
	: dstInfo.getSafeSize(webpRowBytes);
	size_t dstBpp = SkColorTypeBytesPerPixel(dstInfo.colorType());
	size_t webpBpp = needsCopy ? sizeof(uint32_t) : dstBpp;

	size_t offset = dstX * webpBpp + dstY * webpRowBytes;
	config.output.u.RGBA.rgba = SkTAddOffset<uint8_t>(webpDst, offset);
	config.output.u.RGBA.stride = (int) webpRowBytes;
	config.output.u.RGBA.size = totalBytes - offset;

	SkAutoTCallVProc<WebPIDecoder, WebPIDelete> idec(WebPIDecode(nullptr, 0, &config));
	if (!idec) {
	return kInvalidInput;
	}

	int rowsDecoded;
	SkCodec::Result result;
	switch (WebPIUpdate(idec, frame.fragment.bytes, frame.fragment.size)) {
	case VP8_STATUS_OK:
	rowsDecoded = scaledHeight;
	result = kSuccess;
	break;
	case VP8_STATUS_SUSPENDED:
	WebPIDecGetRGB(idec, &rowsDecoded, nullptr, nullptr, nullptr);
	*rowsDecodedPtr = rowsDecoded + dstY;
	result = kIncompleteInput;
	break;
	default:
	return kInvalidInput;
	}

	if (this->colorXform()) {
	SkColorSpaceXform::ColorFormat dstColorFormat = select_xform_format(dstInfo.colorType());
	SkAlphaType xformAlphaType = select_xform_alpha(dstInfo.alphaType(),
	this->getInfo().alphaType());

	uint32_t* xformSrc = (uint32_t*) config.output.u.RGBA.rgba;
	void* xformDst = SkTAddOffset<void>(dst, dstBpp * dstX + rowBytes * dstY);
	size_t srcRowBytes = config.output.u.RGBA.stride;
	for (int y = 0; y < rowsDecoded; y++) {
	SkAssertResult(this->colorXform()->apply(dstColorFormat, xformDst,
	SkColorSpaceXform::kBGRA_8888_ColorFormat, xformSrc, scaledWidth,
	xformAlphaType));
	xformDst = SkTAddOffset<void>(xformDst, rowBytes);
	xformSrc = SkTAddOffset<uint32_t>(xformSrc, srcRowBytes);
	}
	}

	return result;
	}

	SkWebpCodec::SkWebpCodec(int width, int height, const SkEncodedInfo& info,
	sk_sp<SkColorSpace> colorSpace, SkStream* stream, WebPDemuxer* demux,
	sk_sp<SkData> data)
	: INHERITED(width, height, info, stream, std::move(colorSpace))
	, fDemux(demux)
	, fData(std::move(data))
	{}