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/*
* Copyright (c) 2010, Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "PNGImageEncoder.h"
#include "IntSize.h"
#include "SkBitmap.h"
#include "SkColorPriv.h"
#include "SkUnPreMultiply.h"
extern "C" {
#include "png.h"
}
namespace WebCore {
static void writeOutput(png_structp png, png_bytep data, png_size_t size)
{
static_cast<Vector<unsigned char>*>(png->io_ptr)->append(data, size);
}
static void preMultipliedBGRAtoRGBA(const SkPMColor* input, int pixels, unsigned char* output)
{
static const SkUnPreMultiply::Scale* scale = SkUnPreMultiply::GetScaleTable();
for (; pixels-- > 0; ++input) {
const unsigned alpha = SkGetPackedA32(*input);
if ((alpha != 0) && (alpha != 255)) {
*output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedR32(*input));
*output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedG32(*input));
*output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedB32(*input));
*output++ = alpha;
} else {
*output++ = SkGetPackedR32(*input);
*output++ = SkGetPackedG32(*input);
*output++ = SkGetPackedB32(*input);
*output++ = alpha;
}
}
}
bool PNGImageEncoder::encode(const SkBitmap& bitmap, Vector<unsigned char>* output)
{
if (bitmap.config() != SkBitmap::kARGB_8888_Config)
return false; // Only support ARGB 32 bpp skia bitmaps.
SkAutoLockPixels bitmapLock(bitmap);
IntSize imageSize(bitmap.width(), bitmap.height());
imageSize.clampNegativeToZero();
Vector<unsigned char> row;
png_struct* png = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
png_info* info = png_create_info_struct(png);
if (!png || !info || setjmp(png_jmpbuf(png))) {
png_destroy_write_struct(png ? &png : 0, info ? &info : 0);
return false;
}
// Optimize compression for speed.
// The parameters are the same as what libpng uses by default for RGB and RGBA images, except:
// - the zlib compression level is 3 instead of 6, to avoid the lazy Ziv-Lempel match searching;
// - the delta filter is 1 ("sub") instead of 5 ("all"), to reduce the filter computations.
// The zlib memory level (8) and strategy (Z_FILTERED) will be set inside libpng.
//
// Avoid the zlib strategies Z_HUFFMAN_ONLY or Z_RLE.
// Although they are the fastest for poorly-compressible images (e.g. photographs),
// they are very slow for highly-compressible images (e.g. text, drawings or business graphics).
png_set_compression_level(png, 3);
png_set_filter(png, PNG_FILTER_TYPE_BASE, PNG_FILTER_SUB);
png_set_write_fn(png, output, writeOutput, 0);
png_set_IHDR(png, info, imageSize.width(), imageSize.height(),
8, PNG_COLOR_TYPE_RGB_ALPHA, 0, 0, 0);
png_write_info(png, info);
const SkPMColor* pixels = static_cast<SkPMColor*>(bitmap.getPixels());
row.resize(imageSize.width() * bitmap.bytesPerPixel());
for (int y = 0; y < imageSize.height(); ++y) {
preMultipliedBGRAtoRGBA(pixels, imageSize.width(), row.data());
png_write_row(png, row.data());
pixels += imageSize.width();
}
png_write_end(png, info);
png_destroy_write_struct(&png, &info);
return true;
}
} // namespace WebCore
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