/*
* 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) {}