src/codec/SkWebpCodec.cpp - skia.git - Git at Google

 /*
  * 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 "SkWebpCodec.h"
 #include "SkTemplates.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/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.
 static bool webp_parse_header(SkStream* stream, SkImageInfo* info) {
     unsigned char buffer[WEBP_VP8_HEADER_SIZE];
     SkASSERT(WEBP_VP8_HEADER_SIZE <= SkCodec::MinBufferedBytesNeeded());

     const size_t bytesPeeked = stream->peek(buffer, WEBP_VP8_HEADER_SIZE);
     if (bytesPeeked != WEBP_VP8_HEADER_SIZE) {
         // Use read + rewind as a backup
         if (stream->read(buffer, WEBP_VP8_HEADER_SIZE) != WEBP_VP8_HEADER_SIZE
             || !stream->rewind())
         return false;
     }

     WebPBitstreamFeatures features;
     VP8StatusCode status = WebPGetFeatures(buffer, WEBP_VP8_HEADER_SIZE, &features);
     if (VP8_STATUS_OK != status) {
         return false; // Invalid WebP file.
     }

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

     if (info) {
         // FIXME: Is N32 the right type?
         // Is unpremul the right type? Clients of SkCodec may assume it's the
         // best type, when Skia currently cannot draw unpremul (and raster is faster
         // with premul).
         *info = SkImageInfo::Make(features.width, features.height, kN32_SkColorType,
                                   SkToBool(features.has_alpha) ? kUnpremul_SkAlphaType
                                                               : kOpaque_SkAlphaType);
     }
     return true;
 }

 SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
     SkAutoTDelete<SkStream> streamDeleter(stream);
     SkImageInfo info;
     if (webp_parse_header(stream, &info)) {
         return new SkWebpCodec(info, streamDeleter.detach());
     }
     return nullptr;
 }

 // This version is slightly different from SkCodecPriv's version of conversion_possible. It
 // supports both byte orders for 8888.
 static bool webp_conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {
     if (dst.profileType() != src.profileType()) {
         return false;
     }

     if (!valid_alpha(dst.alphaType(), src.alphaType())) {
         return false;
     }

     switch (dst.colorType()) {
         // Both byte orders are supported.
         case kBGRA_8888_SkColorType:
         case kRGBA_8888_SkColorType:
             return true;
         case kRGB_565_SkColorType:
             return src.alphaType() == kOpaque_SkAlphaType;
         default:
             return false;
     }
 }

 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;
     }
 }

 // The WebP decoding API allows us to incrementally pass chunks of bytes as we receive them to the
 // decoder with WebPIAppend. In order to do so, we need to read chunks from the SkStream. This size
 // is arbitrary.
 static const size_t BUFFER_SIZE = 4096;

 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* rowsDecoded) {
     if (!webp_conversion_possible(dstInfo, this->getInfo())) {
         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));

     SkIRect bounds = SkIRect::MakeSize(this->getInfo().dimensions());
     if (options.fSubset) {
         // Caller is requesting a subset.
         if (!bounds.contains(*options.fSubset)) {
             // The subset is out of bounds.
             return kInvalidParameters;
         }

         bounds = *options.fSubset;

         // This is tricky. libwebp snaps the top and left to even values. We could let libwebp
         // do the snap, and return a subset which is a different one than requested. The problem
         // with that approach is that the caller may try to stitch subsets together, and if we
         // returned different subsets than requested, there would be artifacts at the boundaries.
         // Instead, we report that we cannot support odd values for top and left..
         if (!SkIsAlign2(bounds.fLeft) || !SkIsAlign2(bounds.fTop)) {
             return kInvalidParameters;
         }

 #ifdef SK_DEBUG
         {
             // Make a copy, since getValidSubset can change its input.
             SkIRect subset(bounds);
             // That said, getValidSubset should *not* change its input, in this case; otherwise
             // getValidSubset does not match the actual subsets we can do.
             SkASSERT(this->getValidSubset(&subset) && subset == bounds);
         }
 #endif

         config.options.use_cropping = 1;
         config.options.crop_left = bounds.fLeft;
         config.options.crop_top = bounds.fTop;
         config.options.crop_width = bounds.width();
         config.options.crop_height = bounds.height();
     }

     SkISize dstDimensions = dstInfo.dimensions();
     if (bounds.size() != dstDimensions) {
         // Caller is requesting scaling.
         config.options.use_scaling = 1;
         config.options.scaled_width = dstDimensions.width();
         config.options.scaled_height = dstDimensions.height();
     }

     config.output.colorspace = webp_decode_mode(dstInfo.colorType(),
             dstInfo.alphaType() == kPremul_SkAlphaType);
     config.output.u.RGBA.rgba = (uint8_t*) dst;
     config.output.u.RGBA.stride = (int) rowBytes;
     config.output.u.RGBA.size = dstInfo.getSafeSize(rowBytes);
     config.output.is_external_memory = 1;

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

     SkAutoTMalloc<uint8_t> storage(BUFFER_SIZE);
     uint8_t* buffer = storage.get();
     while (true) {
         const size_t bytesRead = stream()->read(buffer, BUFFER_SIZE);
         if (0 == bytesRead) {
             WebPIDecGetRGB(idec, rowsDecoded, NULL, NULL, NULL);
             return kIncompleteInput;
         }

         switch (WebPIAppend(idec, buffer, bytesRead)) {
             case VP8_STATUS_OK:
                 return kSuccess;
             case VP8_STATUS_SUSPENDED:
                 // Break out of the switch statement. Continue the loop.
                 break;
             default:
                 return kInvalidInput;
         }
     }
 }

 SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
     : INHERITED(info, stream) {}
	/*
	* 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 "SkWebpCodec.h"
	#include "SkTemplates.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/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.
	static bool webp_parse_header(SkStream* stream, SkImageInfo* info) {
	unsigned char buffer[WEBP_VP8_HEADER_SIZE];
	SkASSERT(WEBP_VP8_HEADER_SIZE <= SkCodec::MinBufferedBytesNeeded());

	const size_t bytesPeeked = stream->peek(buffer, WEBP_VP8_HEADER_SIZE);
	if (bytesPeeked != WEBP_VP8_HEADER_SIZE) {
	// Use read + rewind as a backup
	if (stream->read(buffer, WEBP_VP8_HEADER_SIZE) != WEBP_VP8_HEADER_SIZE
	\|\| !stream->rewind())
	return false;
	}

	WebPBitstreamFeatures features;
	VP8StatusCode status = WebPGetFeatures(buffer, WEBP_VP8_HEADER_SIZE, &features);
	if (VP8_STATUS_OK != status) {
	return false; // Invalid WebP file.
	}

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

	if (info) {
	// FIXME: Is N32 the right type?
	// Is unpremul the right type? Clients of SkCodec may assume it's the
	// best type, when Skia currently cannot draw unpremul (and raster is faster
	// with premul).
	*info = SkImageInfo::Make(features.width, features.height, kN32_SkColorType,
	SkToBool(features.has_alpha) ? kUnpremul_SkAlphaType
	: kOpaque_SkAlphaType);
	}
	return true;
	}

	SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
	SkAutoTDelete<SkStream> streamDeleter(stream);
	SkImageInfo info;
	if (webp_parse_header(stream, &info)) {
	return new SkWebpCodec(info, streamDeleter.detach());
	}
	return nullptr;
	}

	// This version is slightly different from SkCodecPriv's version of conversion_possible. It
	// supports both byte orders for 8888.
	static bool webp_conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {
	if (dst.profileType() != src.profileType()) {
	return false;
	}

	if (!valid_alpha(dst.alphaType(), src.alphaType())) {
	return false;
	}

	switch (dst.colorType()) {
	// Both byte orders are supported.
	case kBGRA_8888_SkColorType:
	case kRGBA_8888_SkColorType:
	return true;
	case kRGB_565_SkColorType:
	return src.alphaType() == kOpaque_SkAlphaType;
	default:
	return false;
	}
	}

	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;
	}
	}

	// The WebP decoding API allows us to incrementally pass chunks of bytes as we receive them to the
	// decoder with WebPIAppend. In order to do so, we need to read chunks from the SkStream. This size
	// is arbitrary.
	static const size_t BUFFER_SIZE = 4096;

	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* rowsDecoded) {
	if (!webp_conversion_possible(dstInfo, this->getInfo())) {
	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));

	SkIRect bounds = SkIRect::MakeSize(this->getInfo().dimensions());
	if (options.fSubset) {
	// Caller is requesting a subset.
	if (!bounds.contains(*options.fSubset)) {
	// The subset is out of bounds.
	return kInvalidParameters;
	}

	bounds = *options.fSubset;

	// This is tricky. libwebp snaps the top and left to even values. We could let libwebp
	// do the snap, and return a subset which is a different one than requested. The problem
	// with that approach is that the caller may try to stitch subsets together, and if we
	// returned different subsets than requested, there would be artifacts at the boundaries.
	// Instead, we report that we cannot support odd values for top and left..
	if (!SkIsAlign2(bounds.fLeft) \|\| !SkIsAlign2(bounds.fTop)) {
	return kInvalidParameters;
	}

	#ifdef SK_DEBUG
	{
	// Make a copy, since getValidSubset can change its input.
	SkIRect subset(bounds);
	// That said, getValidSubset should not change its input, in this case; otherwise
	// getValidSubset does not match the actual subsets we can do.
	SkASSERT(this->getValidSubset(&subset) && subset == bounds);
	}
	#endif

	config.options.use_cropping = 1;
	config.options.crop_left = bounds.fLeft;
	config.options.crop_top = bounds.fTop;
	config.options.crop_width = bounds.width();
	config.options.crop_height = bounds.height();
	}

	SkISize dstDimensions = dstInfo.dimensions();
	if (bounds.size() != dstDimensions) {
	// Caller is requesting scaling.
	config.options.use_scaling = 1;
	config.options.scaled_width = dstDimensions.width();
	config.options.scaled_height = dstDimensions.height();
	}

	config.output.colorspace = webp_decode_mode(dstInfo.colorType(),
	dstInfo.alphaType() == kPremul_SkAlphaType);
	config.output.u.RGBA.rgba = (uint8_t*) dst;
	config.output.u.RGBA.stride = (int) rowBytes;
	config.output.u.RGBA.size = dstInfo.getSafeSize(rowBytes);
	config.output.is_external_memory = 1;

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

	SkAutoTMalloc<uint8_t> storage(BUFFER_SIZE);
	uint8_t* buffer = storage.get();
	while (true) {
	const size_t bytesRead = stream()->read(buffer, BUFFER_SIZE);
	if (0 == bytesRead) {
	WebPIDecGetRGB(idec, rowsDecoded, NULL, NULL, NULL);
	return kIncompleteInput;
	}

	switch (WebPIAppend(idec, buffer, bytesRead)) {
	case VP8_STATUS_OK:
	return kSuccess;
	case VP8_STATUS_SUSPENDED:
	// Break out of the switch statement. Continue the loop.
	break;
	default:
	return kInvalidInput;
	}
	}
	}

	SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
	: INHERITED(info, stream) {}