| // 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. |
| |
| // This is a duplicate of chromium's src/tools/imagediff/image_diff_png.cc |
| // that has been modified to build in a pdfium environment, which itself |
| // was duplicated as follows: |
| |
| // This is a duplicate of ui/gfx/codec/png_codec.cc, after removing code related |
| // to Skia, that we can use when running layout tests with minimal dependencies. |
| |
| #include "testing/image_diff/image_diff_png.h" |
| |
| #include <stdlib.h> |
| #include <string.h> |
| |
| #include <string> |
| |
| #include "third_party/base/compiler_specific.h" |
| #include "third_party/base/logging.h" |
| |
| #ifdef USE_SYSTEM_ZLIB |
| #include <zlib.h> |
| #else |
| #include "third_party/zlib/zlib.h" |
| #endif |
| |
| #ifdef USE_SYSTEM_LIBPNG |
| #include <png.h> |
| #else |
| #include "third_party/libpng16/png.h" |
| #endif |
| |
| namespace image_diff_png { |
| |
| namespace { |
| |
| enum ColorFormat { |
| // 3 bytes per pixel (packed), in RGB order regardless of endianness. |
| // This is the native JPEG format. |
| FORMAT_RGB, |
| |
| // 3 bytes per pixel, in BGR order regardless of endianness. |
| FORMAT_BGR, |
| |
| // 4 bytes per pixel, in RGBA order in memory regardless of endianness. |
| FORMAT_RGBA, |
| |
| // 4 bytes per pixel, in BGRA order in memory regardless of endianness. |
| // This is the default Windows DIB order. |
| FORMAT_BGRA, |
| |
| // 1 byte per pixel. |
| FORMAT_GRAY, |
| }; |
| |
| // Represents a comment in the tEXt ancillary chunk of the png. |
| struct Comment { |
| std::string key; |
| std::string text; |
| }; |
| |
| // Converts BGRA->RGBA and RGBA->BGRA. |
| void ConvertBetweenBGRAandRGBA(const uint8_t* input, |
| int pixel_width, |
| uint8_t* output, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &input[x * 4]; |
| uint8_t* pixel_out = &output[x * 4]; |
| pixel_out[0] = pixel_in[2]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[0]; |
| pixel_out[3] = pixel_in[3]; |
| } |
| } |
| |
| void ConvertBGRtoRGB(const uint8_t* bgr, |
| int pixel_width, |
| uint8_t* rgb, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &bgr[x * 3]; |
| uint8_t* pixel_out = &rgb[x * 3]; |
| pixel_out[0] = pixel_in[2]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[0]; |
| } |
| } |
| |
| void ConvertRGBAtoRGB(const uint8_t* rgba, |
| int pixel_width, |
| uint8_t* rgb, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &rgba[x * 4]; |
| uint8_t* pixel_out = &rgb[x * 3]; |
| pixel_out[0] = pixel_in[0]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[2]; |
| } |
| } |
| |
| // Decoder |
| // |
| // This code is based on WebKit libpng interface (PNGImageDecoder), which is |
| // in turn based on the Mozilla png decoder. |
| |
| // Gamma constants: We assume we're on Windows which uses a gamma of 2.2. |
| constexpr double kDefaultGamma = 2.2; |
| |
| // Maximum gamma accepted by PNG library. |
| constexpr double kMaxGamma = 21474.83; |
| |
| constexpr double kInverseGamma = 1.0 / kDefaultGamma; |
| |
| class PngDecoderState { |
| public: |
| PngDecoderState(ColorFormat ofmt, std::vector<uint8_t>* out) |
| : output_format(ofmt), output(out) {} |
| |
| const ColorFormat output_format; |
| int output_channels = 0; |
| |
| // Used during the reading of an SkBitmap. Defaults to true until we see a |
| // pixel with anything other than an alpha of 255. |
| bool is_opaque = true; |
| |
| // An intermediary buffer for decode output. |
| std::vector<uint8_t>* const output; |
| |
| // Called to convert a row from the library to the correct output format. |
| // When null, no conversion is necessary. |
| void (*row_converter)(const uint8_t* in, |
| int w, |
| uint8_t* out, |
| bool* is_opaque) = nullptr; |
| |
| // Size of the image, set in the info callback. |
| int width = 0; |
| int height = 0; |
| |
| // Set to true when we've found the end of the data. |
| bool done = false; |
| }; |
| |
| void ConvertRGBtoRGBA(const uint8_t* rgb, |
| int pixel_width, |
| uint8_t* rgba, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &rgb[x * 3]; |
| uint8_t* pixel_out = &rgba[x * 4]; |
| pixel_out[0] = pixel_in[0]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[2]; |
| pixel_out[3] = 0xff; |
| } |
| } |
| |
| void ConvertRGBtoBGRA(const uint8_t* rgb, |
| int pixel_width, |
| uint8_t* bgra, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &rgb[x * 3]; |
| uint8_t* pixel_out = &bgra[x * 4]; |
| pixel_out[0] = pixel_in[2]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[0]; |
| pixel_out[3] = 0xff; |
| } |
| } |
| |
| // Called when the png header has been read. This code is based on the WebKit |
| // PNGImageDecoder |
| void DecodeInfoCallback(png_struct* png_ptr, png_info* info_ptr) { |
| PngDecoderState* state = |
| static_cast<PngDecoderState*>(png_get_progressive_ptr(png_ptr)); |
| |
| int bit_depth, color_type, interlace_type, compression_type; |
| int filter_type, channels; |
| png_uint_32 w, h; |
| png_get_IHDR(png_ptr, info_ptr, &w, &h, &bit_depth, &color_type, |
| &interlace_type, &compression_type, &filter_type); |
| |
| // Bounds check. When the image is unreasonably big, we'll error out and |
| // end up back at the setjmp call when we set up decoding. "Unreasonably big" |
| // means "big enough that w * h * 32bpp might overflow an int"; we choose this |
| // threshold to match WebKit and because a number of places in code assume |
| // that an image's size (in bytes) fits in a (signed) int. |
| unsigned long long total_size = |
| static_cast<unsigned long long>(w) * static_cast<unsigned long long>(h); |
| if (total_size > ((1 << 29) - 1)) |
| longjmp(png_jmpbuf(png_ptr), 1); |
| state->width = static_cast<int>(w); |
| state->height = static_cast<int>(h); |
| |
| // Expand to ensure we use 24-bit for RGB and 32-bit for RGBA. |
| if (color_type == PNG_COLOR_TYPE_PALETTE || |
| (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)) |
| png_set_expand(png_ptr); |
| |
| // Transparency for paletted images. |
| if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) |
| png_set_expand(png_ptr); |
| |
| // Convert 16-bit to 8-bit. |
| if (bit_depth == 16) |
| png_set_strip_16(png_ptr); |
| |
| // Expand grayscale to RGB. |
| if (color_type == PNG_COLOR_TYPE_GRAY || |
| color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
| png_set_gray_to_rgb(png_ptr); |
| |
| // Deal with gamma and keep it under our control. |
| double gamma; |
| if (png_get_gAMA(png_ptr, info_ptr, &gamma)) { |
| if (gamma <= 0.0 || gamma > kMaxGamma) { |
| gamma = kInverseGamma; |
| png_set_gAMA(png_ptr, info_ptr, gamma); |
| } |
| png_set_gamma(png_ptr, kDefaultGamma, gamma); |
| } else { |
| png_set_gamma(png_ptr, kDefaultGamma, kInverseGamma); |
| } |
| |
| // Tell libpng to send us rows for interlaced pngs. |
| if (interlace_type == PNG_INTERLACE_ADAM7) |
| png_set_interlace_handling(png_ptr); |
| |
| // Update our info now |
| png_read_update_info(png_ptr, info_ptr); |
| channels = png_get_channels(png_ptr, info_ptr); |
| |
| // Pick our row format converter necessary for this data. |
| if (channels == 3) { |
| switch (state->output_format) { |
| case FORMAT_RGB: |
| state->row_converter = nullptr; // no conversion necessary |
| state->output_channels = 3; |
| break; |
| case FORMAT_RGBA: |
| state->row_converter = &ConvertRGBtoRGBA; |
| state->output_channels = 4; |
| break; |
| case FORMAT_BGRA: |
| state->row_converter = &ConvertRGBtoBGRA; |
| state->output_channels = 4; |
| break; |
| case FORMAT_GRAY: |
| state->row_converter = nullptr; |
| state->output_channels = 1; |
| break; |
| default: |
| NOTREACHED(); |
| break; |
| } |
| } else if (channels == 4) { |
| switch (state->output_format) { |
| case FORMAT_RGB: |
| state->row_converter = &ConvertRGBAtoRGB; |
| state->output_channels = 3; |
| break; |
| case FORMAT_RGBA: |
| state->row_converter = nullptr; // no conversion necessary |
| state->output_channels = 4; |
| break; |
| case FORMAT_BGRA: |
| state->row_converter = &ConvertBetweenBGRAandRGBA; |
| state->output_channels = 4; |
| break; |
| default: |
| NOTREACHED(); |
| break; |
| } |
| } else { |
| NOTREACHED(); |
| longjmp(png_jmpbuf(png_ptr), 1); |
| } |
| |
| state->output->resize(state->width * state->output_channels * state->height); |
| } |
| |
| void DecodeRowCallback(png_struct* png_ptr, |
| png_byte* new_row, |
| png_uint_32 row_num, |
| int pass) { |
| PngDecoderState* state = |
| static_cast<PngDecoderState*>(png_get_progressive_ptr(png_ptr)); |
| |
| if (static_cast<int>(row_num) > state->height) { |
| NOTREACHED(); |
| return; |
| } |
| |
| uint8_t* base = nullptr; |
| base = &state->output->front(); |
| |
| uint8_t* dest = &base[state->width * state->output_channels * row_num]; |
| if (state->row_converter) |
| state->row_converter(new_row, state->width, dest, &state->is_opaque); |
| else |
| memcpy(dest, new_row, state->width * state->output_channels); |
| } |
| |
| void DecodeEndCallback(png_struct* png_ptr, png_info* info) { |
| PngDecoderState* state = |
| static_cast<PngDecoderState*>(png_get_progressive_ptr(png_ptr)); |
| |
| // Mark the image as complete, this will tell the Decode function that we |
| // have successfully found the end of the data. |
| state->done = true; |
| } |
| |
| // Automatically destroys the given read structs on destruction to make |
| // cleanup and error handling code cleaner. |
| class PngReadStructDestroyer { |
| public: |
| PngReadStructDestroyer(png_struct** ps, png_info** pi) : ps_(ps), pi_(pi) {} |
| ~PngReadStructDestroyer() { png_destroy_read_struct(ps_, pi_, nullptr); } |
| |
| private: |
| png_struct** ps_; |
| png_info** pi_; |
| }; |
| |
| bool BuildPNGStruct(pdfium::span<const uint8_t> input, |
| png_struct** png_ptr, |
| png_info** info_ptr) { |
| if (input.size() < 8) |
| return false; // Input data too small to be a png |
| |
| // Have libpng check the signature, it likes the first 8 bytes. |
| if (png_sig_cmp(const_cast<uint8_t*>(input.data()), 0, 8) != 0) |
| return false; |
| |
| *png_ptr = |
| png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr); |
| if (!*png_ptr) |
| return false; |
| |
| *info_ptr = png_create_info_struct(*png_ptr); |
| if (!*info_ptr) { |
| png_destroy_read_struct(png_ptr, nullptr, nullptr); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| std::vector<uint8_t> Decode(pdfium::span<const uint8_t> input, |
| ColorFormat format, |
| int* w, |
| int* h) { |
| std::vector<uint8_t> output; |
| png_struct* png_ptr = nullptr; |
| png_info* info_ptr = nullptr; |
| if (!BuildPNGStruct(input, &png_ptr, &info_ptr)) |
| return output; |
| |
| PngReadStructDestroyer destroyer(&png_ptr, &info_ptr); |
| if (setjmp(png_jmpbuf(png_ptr))) { |
| // The destroyer will ensure that the structures are cleaned up in this |
| // case, even though we may get here as a jump from random parts of the |
| // PNG library called below. |
| return output; |
| } |
| |
| PngDecoderState state(format, &output); |
| |
| png_set_progressive_read_fn(png_ptr, &state, &DecodeInfoCallback, |
| &DecodeRowCallback, &DecodeEndCallback); |
| png_process_data(png_ptr, info_ptr, const_cast<uint8_t*>(input.data()), |
| input.size()); |
| |
| if (!state.done) { |
| // Fed it all the data but the library didn't think we got all the data, so |
| // this file must be truncated. |
| output.clear(); |
| return output; |
| } |
| |
| *w = state.width; |
| *h = state.height; |
| return output; |
| } |
| |
| // Encoder |
| // |
| // This section of the code is based on nsPNGEncoder.cpp in Mozilla |
| // (Copyright 2005 Google Inc.) |
| |
| // Passed around as the io_ptr in the png structs so our callbacks know where |
| // to write data. |
| struct PngEncoderState { |
| explicit PngEncoderState(std::vector<uint8_t>* o) : out(o) {} |
| std::vector<uint8_t>* out; |
| }; |
| |
| // Called by libpng to flush its internal buffer to ours. |
| void EncoderWriteCallback(png_structp png, png_bytep data, png_size_t size) { |
| PngEncoderState* state = static_cast<PngEncoderState*>(png_get_io_ptr(png)); |
| size_t old_size = state->out->size(); |
| state->out->resize(old_size + size); |
| memcpy(&(*state->out)[old_size], data, size); |
| } |
| |
| void FakeFlushCallback(png_structp png) { |
| // We don't need to perform any flushing since we aren't doing real IO, but |
| // we're required to provide this function by libpng. |
| } |
| |
| void ConvertBGRAtoRGB(const uint8_t* bgra, |
| int pixel_width, |
| uint8_t* rgb, |
| bool* is_opaque) { |
| for (int x = 0; x < pixel_width; x++) { |
| const uint8_t* pixel_in = &bgra[x * 4]; |
| uint8_t* pixel_out = &rgb[x * 3]; |
| pixel_out[0] = pixel_in[2]; |
| pixel_out[1] = pixel_in[1]; |
| pixel_out[2] = pixel_in[0]; |
| } |
| } |
| |
| #ifdef PNG_TEXT_SUPPORTED |
| |
| inline char* strdup(const char* str) { |
| #if defined(OS_WIN) |
| return _strdup(str); |
| #else |
| return ::strdup(str); |
| #endif |
| } |
| |
| class CommentWriter { |
| public: |
| explicit CommentWriter(const std::vector<Comment>& comments) |
| : comments_(comments), png_text_(new png_text[comments.size()]) { |
| for (size_t i = 0; i < comments.size(); ++i) |
| AddComment(i, comments[i]); |
| } |
| |
| ~CommentWriter() { |
| for (size_t i = 0; i < comments_.size(); ++i) { |
| free(png_text_[i].key); |
| free(png_text_[i].text); |
| } |
| delete[] png_text_; |
| } |
| |
| bool HasComments() { return !comments_.empty(); } |
| |
| png_text* get_png_text() { return png_text_; } |
| |
| int size() { return static_cast<int>(comments_.size()); } |
| |
| private: |
| void AddComment(size_t pos, const Comment& comment) { |
| png_text_[pos].compression = PNG_TEXT_COMPRESSION_NONE; |
| // A PNG comment's key can only be 79 characters long. |
| if (comment.key.length() > 79) |
| return; |
| png_text_[pos].key = strdup(comment.key.substr(0, 78).c_str()); |
| png_text_[pos].text = strdup(comment.text.c_str()); |
| png_text_[pos].text_length = comment.text.length(); |
| #ifdef PNG_iTXt_SUPPORTED |
| png_text_[pos].itxt_length = 0; |
| png_text_[pos].lang = 0; |
| png_text_[pos].lang_key = 0; |
| #endif |
| } |
| |
| const std::vector<Comment> comments_; |
| png_text* png_text_; |
| }; |
| #endif // PNG_TEXT_SUPPORTED |
| |
| // The type of functions usable for converting between pixel formats. |
| typedef void (*FormatConverter)(const uint8_t* in, |
| int w, |
| uint8_t* out, |
| bool* is_opaque); |
| |
| // libpng uses a wacky setjmp-based API, which makes the compiler nervous. |
| // We constrain all of the calls we make to libpng where the setjmp() is in |
| // place to this function. |
| // Returns true on success. |
| bool DoLibpngWrite(png_struct* png_ptr, |
| png_info* info_ptr, |
| PngEncoderState* state, |
| int width, |
| int height, |
| int row_byte_width, |
| pdfium::span<const uint8_t> input, |
| int compression_level, |
| int png_output_color_type, |
| int output_color_components, |
| FormatConverter converter, |
| const std::vector<Comment>& comments) { |
| #ifdef PNG_TEXT_SUPPORTED |
| CommentWriter comment_writer(comments); |
| #endif |
| uint8_t* row_buffer = nullptr; |
| |
| // Make sure to not declare any locals here -- locals in the presence |
| // of setjmp() in C++ code makes gcc complain. |
| |
| if (setjmp(png_jmpbuf(png_ptr))) { |
| delete[] row_buffer; |
| return false; |
| } |
| |
| png_set_compression_level(png_ptr, compression_level); |
| |
| // Set our callback for libpng to give us the data. |
| png_set_write_fn(png_ptr, state, EncoderWriteCallback, FakeFlushCallback); |
| |
| png_set_IHDR(png_ptr, info_ptr, width, height, 8, png_output_color_type, |
| PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, |
| PNG_FILTER_TYPE_DEFAULT); |
| |
| #ifdef PNG_TEXT_SUPPORTED |
| if (comment_writer.HasComments()) { |
| png_set_text(png_ptr, info_ptr, comment_writer.get_png_text(), |
| comment_writer.size()); |
| } |
| #endif |
| |
| png_write_info(png_ptr, info_ptr); |
| |
| if (!converter) { |
| // No conversion needed, give the data directly to libpng. |
| for (int y = 0; y < height; y++) { |
| png_write_row(png_ptr, const_cast<uint8_t*>(&input[y * row_byte_width])); |
| } |
| } else { |
| // Needs conversion using a separate buffer. |
| row_buffer = new uint8_t[width * output_color_components]; |
| for (int y = 0; y < height; y++) { |
| converter(&input[y * row_byte_width], width, row_buffer, nullptr); |
| png_write_row(png_ptr, row_buffer); |
| } |
| delete[] row_buffer; |
| } |
| |
| png_write_end(png_ptr, info_ptr); |
| return true; |
| } |
| |
| std::vector<uint8_t> EncodeWithCompressionLevel( |
| pdfium::span<const uint8_t> input, |
| ColorFormat format, |
| const int width, |
| const int height, |
| int row_byte_width, |
| bool discard_transparency, |
| const std::vector<Comment>& comments, |
| int compression_level) { |
| std::vector<uint8_t> output; |
| |
| // Run to convert an input row into the output row format, nullptr means no |
| // conversion is necessary. |
| FormatConverter converter = nullptr; |
| |
| int input_color_components; |
| int output_color_components; |
| int png_output_color_type; |
| switch (format) { |
| case FORMAT_BGR: |
| converter = ConvertBGRtoRGB; |
| FALLTHROUGH; |
| |
| case FORMAT_RGB: |
| input_color_components = 3; |
| output_color_components = 3; |
| png_output_color_type = PNG_COLOR_TYPE_RGB; |
| break; |
| |
| case FORMAT_RGBA: |
| input_color_components = 4; |
| if (discard_transparency) { |
| output_color_components = 3; |
| png_output_color_type = PNG_COLOR_TYPE_RGB; |
| converter = ConvertRGBAtoRGB; |
| } else { |
| output_color_components = 4; |
| png_output_color_type = PNG_COLOR_TYPE_RGB_ALPHA; |
| converter = nullptr; |
| } |
| break; |
| |
| case FORMAT_BGRA: |
| input_color_components = 4; |
| if (discard_transparency) { |
| output_color_components = 3; |
| png_output_color_type = PNG_COLOR_TYPE_RGB; |
| converter = ConvertBGRAtoRGB; |
| } else { |
| output_color_components = 4; |
| png_output_color_type = PNG_COLOR_TYPE_RGB_ALPHA; |
| converter = ConvertBetweenBGRAandRGBA; |
| } |
| break; |
| |
| case FORMAT_GRAY: |
| input_color_components = 1; |
| output_color_components = 1; |
| png_output_color_type = PNG_COLOR_TYPE_GRAY; |
| break; |
| |
| default: |
| NOTREACHED(); |
| return output; |
| } |
| |
| // Row stride should be at least as long as the length of the data. |
| if (row_byte_width < input_color_components * width) |
| return output; |
| |
| png_struct* png_ptr = |
| png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr); |
| if (!png_ptr) |
| return output; |
| png_info* info_ptr = png_create_info_struct(png_ptr); |
| if (!info_ptr) { |
| png_destroy_write_struct(&png_ptr, nullptr); |
| return output; |
| } |
| |
| PngEncoderState state(&output); |
| bool success = |
| DoLibpngWrite(png_ptr, info_ptr, &state, width, height, row_byte_width, |
| input, compression_level, png_output_color_type, |
| output_color_components, converter, comments); |
| png_destroy_write_struct(&png_ptr, &info_ptr); |
| |
| if (!success) |
| output.clear(); |
| return output; |
| } |
| |
| std::vector<uint8_t> Encode(pdfium::span<const uint8_t> input, |
| ColorFormat format, |
| const int width, |
| const int height, |
| int row_byte_width, |
| bool discard_transparency, |
| const std::vector<Comment>& comments) { |
| return EncodeWithCompressionLevel(input, format, width, height, |
| row_byte_width, discard_transparency, |
| comments, Z_DEFAULT_COMPRESSION); |
| } |
| |
| } // namespace |
| |
| std::vector<uint8_t> DecodePNG(pdfium::span<const uint8_t> input, |
| bool reverse_byte_order, |
| int* width, |
| int* height) { |
| ColorFormat format = reverse_byte_order ? FORMAT_BGRA : FORMAT_RGBA; |
| return Decode(input, format, width, height); |
| } |
| |
| std::vector<uint8_t> EncodeBGRPNG(pdfium::span<const uint8_t> input, |
| int width, |
| int height, |
| int row_byte_width) { |
| return Encode(input, FORMAT_BGR, width, height, row_byte_width, false, |
| std::vector<Comment>()); |
| } |
| |
| std::vector<uint8_t> EncodeRGBAPNG(pdfium::span<const uint8_t> input, |
| int width, |
| int height, |
| int row_byte_width) { |
| return Encode(input, FORMAT_RGBA, width, height, row_byte_width, false, |
| std::vector<Comment>()); |
| } |
| |
| std::vector<uint8_t> EncodeBGRAPNG(pdfium::span<const uint8_t> input, |
| int width, |
| int height, |
| int row_byte_width, |
| bool discard_transparency) { |
| return Encode(input, FORMAT_BGRA, width, height, row_byte_width, |
| discard_transparency, std::vector<Comment>()); |
| } |
| |
| std::vector<uint8_t> EncodeGrayPNG(pdfium::span<const uint8_t> input, |
| int width, |
| int height, |
| int row_byte_width) { |
| return Encode(input, FORMAT_GRAY, width, height, row_byte_width, false, |
| std::vector<Comment>()); |
| } |
| |
| } // namespace image_diff_png |