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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/webp_transcode/webp_decoder.h"
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#include "base/logging.h"
#include "base/metrics/histogram.h"
namespace {
const uint8_t kNumIfdEntries = 15;
const unsigned int kExtraDataSize = 16;
// 10b for signature/header + n * 12b entries + 4b for IFD terminator:
const unsigned int kExtraDataOffset = 10 + 12 * kNumIfdEntries + 4;
const unsigned int kHeaderSize = kExtraDataOffset + kExtraDataSize;
const int kRecompressionThreshold = 64 * 64; // Threshold in pixels.
const CGFloat kJpegQuality = 0.85;
// Adapted from libwebp example dwebp.c.
void PutLE16(uint8_t* const dst, uint32_t value) {
dst[0] = (value >> 0) & 0xff;
dst[1] = (value >> 8) & 0xff;
}
void PutLE32(uint8_t* const dst, uint32_t value) {
PutLE16(dst + 0, (value >> 0) & 0xffff);
PutLE16(dst + 2, (value >> 16) & 0xffff);
}
void WriteTiffHeader(uint8_t* dst,
int width,
int height,
int bytes_per_px,
bool has_alpha) {
// For non-alpha case, we omit tag 0x152 (ExtraSamples).
const uint8_t num_ifd_entries =
has_alpha ? kNumIfdEntries : kNumIfdEntries - 1;
uint8_t tiff_header[kHeaderSize] = {
0x49, 0x49, 0x2a, 0x00, // little endian signature
8, 0, 0, 0, // offset to the unique IFD that follows
// IFD (offset = 8). Entries must be written in increasing tag order.
num_ifd_entries, 0, // Number of entries in the IFD (12 bytes each).
0x00, 0x01, 3, 0, 1, 0, 0, 0, 0, 0, 0, 0, // 10: Width (TBD)
0x01, 0x01, 3, 0, 1, 0, 0, 0, 0, 0, 0, 0, // 22: Height (TBD)
0x02, 0x01, 3, 0, bytes_per_px, 0, 0, 0, // 34: BitsPerSample: 8888
kExtraDataOffset + 0, 0, 0, 0,
0x03, 0x01, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, // 46: Compression: none
0x06, 0x01, 3, 0, 1, 0, 0, 0, 2, 0, 0, 0, // 58: Photometric: RGB
0x11, 0x01, 4, 0, 1, 0, 0, 0, // 70: Strips offset:
kHeaderSize, 0, 0, 0, // data follows header
0x12, 0x01, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, // 82: Orientation: topleft
0x15, 0x01, 3, 0, 1, 0, 0, 0, // 94: SamplesPerPixels
bytes_per_px, 0, 0, 0,
0x16, 0x01, 3, 0, 1, 0, 0, 0, 0, 0, 0, 0, // 106: Rows per strip (TBD)
0x17, 0x01, 4, 0, 1, 0, 0, 0, 0, 0, 0, 0, // 118: StripByteCount (TBD)
0x1a, 0x01, 5, 0, 1, 0, 0, 0, // 130: X-resolution
kExtraDataOffset + 8, 0, 0, 0,
0x1b, 0x01, 5, 0, 1, 0, 0, 0, // 142: Y-resolution
kExtraDataOffset + 8, 0, 0, 0,
0x1c, 0x01, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, // 154: PlanarConfiguration
0x28, 0x01, 3, 0, 1, 0, 0, 0, 2, 0, 0, 0, // 166: ResolutionUnit (inch)
0x52, 0x01, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, // 178: ExtraSamples: rgbA
0, 0, 0, 0, // 190: IFD terminator
// kExtraDataOffset:
8, 0, 8, 0, 8, 0, 8, 0, // BitsPerSample
72, 0, 0, 0, 1, 0, 0, 0 // 72 pixels/inch, for X/Y-resolution
};
// Fill placeholders in IFD:
PutLE32(tiff_header + 10 + 8, width);
PutLE32(tiff_header + 22 + 8, height);
PutLE32(tiff_header + 106 + 8, height);
PutLE32(tiff_header + 118 + 8, width * bytes_per_px * height);
if (!has_alpha)
PutLE32(tiff_header + 178, 0);
memcpy(dst, tiff_header, kHeaderSize);
}
} // namespace
namespace webp_transcode {
// static
size_t WebpDecoder::GetHeaderSize() {
return kHeaderSize;
}
WebpDecoder::WebpDecoder(WebpDecoder::Delegate* delegate)
: delegate_(delegate), state_(READING_FEATURES), has_alpha_(0) {
DCHECK(delegate_.get());
const bool rv = WebPInitDecoderConfig(&config_);
DCHECK(rv);
}
WebpDecoder::~WebpDecoder() {
WebPFreeDecBuffer(&config_.output);
}
void WebpDecoder::OnDataReceived(const base::scoped_nsobject<NSData>& data) {
DCHECK(data);
switch (state_) {
case READING_FEATURES:
DoReadFeatures(data);
break;
case READING_DATA:
DoReadData(data);
break;
case DONE:
DLOG(WARNING) << "Received WebP data but decoding is finished. Ignoring.";
break;
}
}
void WebpDecoder::Stop() {
if (state_ != DONE) {
state_ = DONE;
DLOG(WARNING) << "Unexpected end of WebP data.";
delegate_->OnFinishedDecoding(false);
}
}
void WebpDecoder::DoReadFeatures(NSData* data) {
DCHECK_EQ(READING_FEATURES, state_);
DCHECK(data);
if (features_)
[features_ appendData:data];
else
features_.reset([[NSMutableData alloc] initWithData:data]);
VP8StatusCode status =
WebPGetFeatures(static_cast<const uint8_t*>([features_ bytes]),
[features_ length], &config_.input);
switch (status) {
case VP8_STATUS_OK: {
has_alpha_ = config_.input.has_alpha;
const uint32_t width = config_.input.width;
const uint32_t height = config_.input.height;
const size_t bytes_per_px = has_alpha_ ? 4 : 3;
const int stride = bytes_per_px * width;
const size_t image_data_size = stride * height;
const size_t total_size = image_data_size + kHeaderSize;
// Force pre-multiplied alpha.
config_.output.colorspace = has_alpha_ ? MODE_rgbA : MODE_RGB;
config_.output.u.RGBA.stride = stride;
// Create the output buffer.
config_.output.u.RGBA.size = image_data_size;
uint8_t* dst = static_cast<uint8_t*>(malloc(total_size));
if (!dst) {
DLOG(ERROR) << "Could not allocate WebP decoding buffer (size = "
<< total_size << ").";
delegate_->OnFinishedDecoding(false);
state_ = DONE;
break;
}
WriteTiffHeader(dst, width, height, bytes_per_px, has_alpha_);
output_buffer_.reset([[NSData alloc] initWithBytesNoCopy:dst
length:total_size
freeWhenDone:YES]);
config_.output.is_external_memory = 1;
config_.output.u.RGBA.rgba = dst + kHeaderSize;
// Start decoding.
state_ = READING_DATA;
incremental_decoder_.reset(WebPINewDecoder(&config_.output));
DoReadData(features_);
features_.reset();
break;
}
case VP8_STATUS_NOT_ENOUGH_DATA:
// Do nothing.
break;
default:
DLOG(ERROR) << "Error in WebP image features.";
delegate_->OnFinishedDecoding(false);
state_ = DONE;
break;
}
}
void WebpDecoder::DoReadData(NSData* data) {
DCHECK_EQ(READING_DATA, state_);
DCHECK(incremental_decoder_);
DCHECK(data);
VP8StatusCode status =
WebPIAppend(incremental_decoder_.get(),
static_cast<const uint8_t*>([data bytes]), [data length]);
switch (status) {
case VP8_STATUS_SUSPENDED:
// Do nothing: re-compression to JPEG or PNG cannot be done incrementally.
// Wait for the whole image to be decoded.
break;
case VP8_STATUS_OK: {
bool rv = DoSendData();
DLOG_IF(ERROR, !rv) << "Error in WebP image conversion.";
state_ = DONE;
delegate_->OnFinishedDecoding(rv);
break;
}
default:
DLOG(ERROR) << "Error in WebP image decoding.";
delegate_->OnFinishedDecoding(false);
state_ = DONE;
break;
}
}
bool WebpDecoder::DoSendData() {
DCHECK_EQ(READING_DATA, state_);
int width, height;
uint8_t* data_ptr = WebPIDecGetRGB(incremental_decoder_.get(), nullptr,
&width, &height, nullptr);
if (!data_ptr)
return false;
DCHECK_EQ(static_cast<const uint8_t*>([output_buffer_ bytes]) + kHeaderSize,
data_ptr);
base::scoped_nsobject<NSData> result_data;
// When the WebP image is larger than |kRecompressionThreshold| it is
// compressed to JPEG or PNG. Otherwise, the uncompressed TIFF is used.
DecodedImageFormat format = TIFF;
if (width * height > kRecompressionThreshold) {
base::scoped_nsobject<UIImage> tiff_image(
[[UIImage alloc] initWithData:output_buffer_]);
if (!tiff_image)
return false;
// Compress to PNG if the image is transparent, JPEG otherwise.
// TODO(droger): Use PNG instead of JPEG if the WebP image is lossless.
if (has_alpha_) {
result_data.reset([UIImagePNGRepresentation(tiff_image) retain]);
format = PNG;
} else {
result_data.reset(
[UIImageJPEGRepresentation(tiff_image, kJpegQuality) retain]);
format = JPEG;
}
if (!result_data)
return false;
} else {
result_data.reset([output_buffer_ retain]);
}
UMA_HISTOGRAM_ENUMERATION("WebP.DecodedImageFormat", format,
DECODED_FORMAT_COUNT);
delegate_->SetImageFeatures([result_data length], format);
delegate_->OnDataDecoded(result_data);
output_buffer_.reset();
return true;
}
} // namespace webp_transcode
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