// 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 "image_diff_png.h"
#include <stdlib.h>
#include <string.h>
#include <string>
#include "third_party/base/logging.h"
#include "third_party/lpng_v163/png.h"
#include "third_party/zlib_v128/zlib.h"
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,
// 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,
};
// 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 unsigned char* input, int pixel_width,
unsigned char* output, bool* is_opaque) {
for (int x = 0; x < pixel_width; x++) {
const unsigned char* pixel_in = &input[x * 4];
unsigned char* 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 ConvertRGBAtoRGB(const unsigned char* rgba, int pixel_width,
unsigned char* rgb, bool* is_opaque) {
for (int x = 0; x < pixel_width; x++) {
const unsigned char* pixel_in = &rgba[x * 4];
unsigned char* pixel_out = &rgb[x * 3];
pixel_out[0] = pixel_in[0];
pixel_out[1] = pixel_in[1];
pixel_out[2] = pixel_in[2];
}
}
} // namespace
// Decoder --------------------------------------------------------------------
//
// This code is based on WebKit libpng interface (PNGImageDecoder), which is
// in turn based on the Mozilla png decoder.
namespace {
// Gamma constants: We assume we're on Windows which uses a gamma of 2.2.
const double kMaxGamma = 21474.83; // Maximum gamma accepted by png library.
const double kDefaultGamma = 2.2;
const double kInverseGamma = 1.0 / kDefaultGamma;
class PngDecoderState {
public:
// Output is a vector<unsigned char>.
PngDecoderState(ColorFormat ofmt, std::vector<unsigned char>* o)
: output_format(ofmt),
output_channels(0),
is_opaque(true),
output(o),
row_converter(NULL),
width(0),
height(0),
done(false) {
}
ColorFormat output_format;
int output_channels;
// 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;
// An intermediary buffer for decode output.
std::vector<unsigned char>* output;
// Called to convert a row from the library to the correct output format.
// When NULL, no conversion is necessary.
void (*row_converter)(const unsigned char* in, int w, unsigned char* out,
bool* is_opaque);
// Size of the image, set in the info callback.
int width;
int height;
// Set to true when we've found the end of the data.
bool done;
};
void ConvertRGBtoRGBA(const unsigned char* rgb, int pixel_width,
unsigned char* rgba, bool* is_opaque) {
for (int x = 0; x < pixel_width; x++) {
const unsigned char* pixel_in = &rgb[x * 3];
unsigned char* 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 unsigned char* rgb, int pixel_width,
unsigned char* bgra, bool* is_opaque) {
for (int x = 0; x < pixel_width; x++) {
const unsigned char* pixel_in = &rgb[x * 3];
unsigned char* 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 = NULL; // 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;
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 = NULL; // 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;
}
unsigned char* base = NULL;
base = &state->output->front();
unsigned char* 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_, NULL);
}
private:
png_struct** ps_;
png_info** pi_;
};
bool BuildPNGStruct(const unsigned char* input, size_t input_size,
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<unsigned char*>(input), 0, 8) != 0)
return false;
*png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!*png_ptr)
return false;
*info_ptr = png_create_info_struct(*png_ptr);
if (!*info_ptr) {
png_destroy_read_struct(png_ptr, NULL, NULL);
return false;
}
return true;
}
} // namespace
// static
bool Decode(const unsigned char* input, size_t input_size,
ColorFormat format, std::vector<unsigned char>* output,
int* w, int* h) {
png_struct* png_ptr = NULL;
png_info* info_ptr = NULL;
if (!BuildPNGStruct(input, input_size, &png_ptr, &info_ptr))
return false;
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 false;
}
PngDecoderState state(format, output);
png_set_progressive_read_fn(png_ptr, &state, &DecodeInfoCallback,
&DecodeRowCallback, &DecodeEndCallback);
png_process_data(png_ptr,
info_ptr,
const_cast<unsigned char*>(input),
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 false;
}
*w = state.width;
*h = state.height;
return true;
}
// Encoder --------------------------------------------------------------------
//
// This section of the code is based on nsPNGEncoder.cpp in Mozilla
// (Copyright 2005 Google Inc.)
namespace {
// Passed around as the io_ptr in the png structs so our callbacks know where
// to write data.
struct PngEncoderState {
explicit PngEncoderState(std::vector<unsigned char>* o) : out(o) {}
std::vector<unsigned char>* 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 unsigned char* bgra, int pixel_width,
unsigned char* rgb, bool* is_opaque) {
for (int x = 0; x < pixel_width; x++) {
const unsigned char* pixel_in = &bgra[x * 4];
unsigned char* 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 unsigned char* in, int w,
unsigned char* 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,
const unsigned char* 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
unsigned char* row_buffer = NULL;
// 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<unsigned char*>(&input[y * row_byte_width]));
}
} else {
// Needs conversion using a separate buffer.
row_buffer = new unsigned char[width * output_color_components];
for (int y = 0; y < height; y ++) {
converter(&input[y * row_byte_width], width, row_buffer, NULL);
png_write_row(png_ptr, row_buffer);
}
delete[] row_buffer;
}
png_write_end(png_ptr, info_ptr);
return true;
}
} // namespace
// static
bool EncodeWithCompressionLevel(const unsigned char* 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<unsigned char>* output) {
// Run to convert an input row into the output row format, NULL means no
// conversion is necessary.
FormatConverter converter = NULL;
int input_color_components, output_color_components;
int png_output_color_type;
switch (format) {
case FORMAT_RGB:
input_color_components = 3;
output_color_components = 3;
png_output_color_type = PNG_COLOR_TYPE_RGB;
discard_transparency = false;
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 = NULL;
}
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;
default:
NOTREACHED();
return false;
}
// Row stride should be at least as long as the length of the data.
if (input_color_components * width < row_byte_width)
return false;
png_struct* png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
NULL, NULL, NULL);
if (!png_ptr)
return false;
png_info* info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr) {
png_destroy_write_struct(&png_ptr, NULL);
return false;
}
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);
return success;
}
// static
bool Encode(const unsigned char* input, ColorFormat format,
const int width, const int height, int row_byte_width,
bool discard_transparency,
const std::vector<Comment>& comments,
std::vector<unsigned char>* output) {
return EncodeWithCompressionLevel(input, format, width, height,
row_byte_width,
discard_transparency,
comments, Z_DEFAULT_COMPRESSION,
output);
}
// Decode a PNG into an RGBA pixel array.
bool DecodePNG(const unsigned char* input, size_t input_size,
std::vector<unsigned char>* output,
int* width, int* height) {
return Decode(input, input_size, FORMAT_RGBA, output, width, height);
}
// Encode an RGBA pixel array into a PNG.
bool EncodeRGBAPNG(const unsigned char* input,
int width,
int height,
int row_byte_width,
std::vector<unsigned char>* output) {
return Encode(input, FORMAT_RGBA,
width, height, row_byte_width, false,
std::vector<Comment>(), output);
}
// Encode an BGRA pixel array into a PNG.
bool EncodeBGRAPNG(const unsigned char* input,
int width,
int height,
int row_byte_width,
bool discard_transparency,
std::vector<unsigned char>* output) {
return Encode(input, FORMAT_BGRA,
width, height, row_byte_width, discard_transparency,
std::vector<Comment>(), output);
}
} // image_diff_png