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/*
* Copyright (C) 2011 Research In Motion Limited. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Portions of this file are Copyright 2005 Google Inc.
*/
#include "config.h"
#include "PNGImageEncoder.h"
#include "SkBitmap.h"
#include "SkUnPreMultiply.h"
extern "C" {
#include "png.h"
}
#include <OwnArrayPtr.h>
// This code is almost a mirror of the code in WebCore/platform/image-encoders/skia/PNGImageEncoder.cpp
// since we can't include this private WebCore file in a WebKit-client application.
// Converts BGRA->RGBA and RGBA->BGRA and undoes alpha premultiplication.
static void preMultipliedBGRAtoRGBA(const unsigned char* input, int numberOfPixels, unsigned char* output)
{
SkBitmap inputBitmap;
inputBitmap.setConfig(SkBitmap::kARGB_8888_Config, numberOfPixels, 1);
inputBitmap.setPixels(const_cast<unsigned char*>(input));
for (int x = 0; x < numberOfPixels; x++) {
uint32_t srcPixel = *inputBitmap.getAddr32(x, 0);
SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(srcPixel);
unsigned char* pixelOut = &output[x * 4];
pixelOut[0] = SkColorGetR(unmultiplied);
pixelOut[1] = SkColorGetG(unmultiplied);
pixelOut[2] = SkColorGetB(unmultiplied);
pixelOut[3] = SkColorGetA(unmultiplied);
}
}
// Passed around as the io_ptr in the png structs so our callbacks know where
// to write data.
struct PNGEncoderState {
PNGEncoderState(Vector<unsigned char>* o) : m_out(o) { }
Vector<unsigned char>* m_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));
ASSERT(state->m_out);
size_t oldSize = state->m_out->size();
state->m_out->resize(oldSize + size);
memcpy(&(*state->m_out)[oldSize], data, size);
}
// 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)
: m_pngStruct(ps)
, m_pngInfo(pi)
{
}
~PNGWriteStructDestroyer()
{
png_destroy_write_struct(m_pngStruct, m_pngInfo);
}
private:
png_struct** m_pngStruct;
png_info** m_pngInfo;
};
typedef void (*PixelConversionFunc)(const unsigned char*, int, unsigned char*);
static bool encodeImpl(const unsigned char* input, int imageWidth, int imageHeight, int bytesPerRow, Vector<unsigned char>* output, PixelConversionFunc conversionFunc)
{
int inputColorComponents = 4;
int outputColorComponents = 4;
int pngOutputColorType = PNG_COLOR_TYPE_RGB_ALPHA;
if (imageWidth < 0)
imageWidth = 0;
if (imageHeight < 0)
imageHeight = 0;
// Row stride should be at least as long as the length of the data.
if (inputColorComponents * imageWidth > bytesPerRow) {
ASSERT(false);
return false;
}
png_struct* pngPtr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if (!pngPtr)
return false;
png_info* infoPtr = png_create_info_struct(pngPtr);
if (!infoPtr) {
png_destroy_write_struct(&pngPtr, 0);
return false;
}
PNGWriteStructDestroyer destroyer(&pngPtr, &infoPtr);
if (setjmp(png_jmpbuf(pngPtr))) {
// 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(pngPtr, &state, encoderWriteCallback, 0);
png_set_IHDR(pngPtr, infoPtr, imageWidth, imageHeight, 8, pngOutputColorType,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_write_info(pngPtr, infoPtr);
OwnArrayPtr<unsigned char> rowPixels = adoptArrayPtr(new unsigned char[imageWidth * outputColorComponents]);
for (int y = 0; y < imageHeight; y ++) {
conversionFunc(&input[y * bytesPerRow], imageWidth, rowPixels.get());
png_write_row(pngPtr, rowPixels.get());
}
png_write_end(pngPtr, infoPtr);
return true;
}
bool encodeSkBitmapToPNG(const SkBitmap& image, Vector<unsigned char>* output)
{
if (image.config() != SkBitmap::kARGB_8888_Config)
return false; // Only support ARGB at 8 bpp now.
image.lockPixels();
bool result = encodeImpl(static_cast<unsigned char*>(image.getPixels()), image.width(), image.height(), image.rowBytes(), output, preMultipliedBGRAtoRGBA);
image.unlockPixels();
return result;
}
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