// Copyright (c) 2006-2008 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 "base/basictypes.h"
#include "base/gfx/png_encoder.h"
#include "base/logging.h"
#include "skia/include/SkBitmap.h"
extern "C" {
#include "png.h"
}
namespace {
// Converts BGRA->RGBA and RGBA->BGRA.
void ConvertBetweenBGRAandRGBA(const unsigned char* input, int pixel_width,
unsigned char* output) {
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) {
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
// 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 {
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));
DCHECK(state->out);
size_t old_size = state->out->size();
state->out->resize(old_size + size);
memcpy(&(*state->out)[old_size], data, size);
}
void ConvertBGRAtoRGB(const unsigned char* bgra, int pixel_width,
unsigned char* rgb) {
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];
}
}
// Automatically destroys the given write structs on destruction to make
// cleanup and error handling code cleaner.
class PngWriteStructDestroyer {
public:
PngWriteStructDestroyer(png_struct** ps, png_info** pi) : ps_(ps), pi_(pi) {
}
~PngWriteStructDestroyer() {
png_destroy_write_struct(ps_, pi_);
}
private:
png_struct** ps_;
png_info** pi_;
DISALLOW_EVIL_CONSTRUCTORS(PngWriteStructDestroyer);
};
} // namespace
// static
bool PNGEncoder::Encode(const unsigned char* input, ColorFormat format,
int w, int h, int row_byte_width,
bool discard_transparency,
std::vector<unsigned char>* output) {
// Run to convert an input row into the output row format, NULL means no
// conversion is necessary.
void (*converter)(const unsigned char* in, int w, unsigned char* out) = 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() << "Unknown pixel format";
return false;
}
// Row stride should be at least as long as the length of the data.
DCHECK(input_color_components * w <= row_byte_width);
png_struct* png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
png_voidp_NULL,
png_error_ptr_NULL,
png_error_ptr_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;
}
PngWriteStructDestroyer 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;
}
// Set our callback for libpng to give us the data.
PngEncoderState state(output);
png_set_write_fn(png_ptr, &state, EncoderWriteCallback, NULL);
png_set_IHDR(png_ptr, info_ptr, w, h, 8, png_output_color_type,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_write_info(png_ptr, info_ptr);
if (!converter) {
// No conversion needed, give the data directly to libpng.
for (int y = 0; y < h; y ++)
png_write_row(png_ptr, const_cast<unsigned char*>(&input[y * row_byte_width]));
} else {
// Needs conversion using a separate buffer.
unsigned char* row = new unsigned char[w * output_color_components];
for (int y = 0; y < h; y ++) {
converter(&input[y * row_byte_width], w, row);
png_write_row(png_ptr, row);
}
delete[] row;
}
png_write_end(png_ptr, info_ptr);
return true;
}
// static
bool PNGEncoder::EncodeBGRASkBitmap(const SkBitmap& input,
bool discard_transparency,
std::vector<unsigned char>* output) {
SkAutoLockPixels input_lock(input);
DCHECK(input.empty() || input.bytesPerPixel() == 4);
return Encode(static_cast<unsigned char*>(input.getPixels()),
PNGEncoder::FORMAT_BGRA, input.width(), input.height(),
input.rowBytes(), discard_transparency, output);
}