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32 #include "PNGImageEncoder.h"
34 #include "ImageData.h"
37 #include "SkColorPriv.h"
38 #include "SkUnPreMultiply.h"
45 static void writeOutput(png_structp png, png_bytep data, png_size_t size)
47 static_cast<Vector<unsigned char>*>(png_get_io_ptr(png))->append(data, size);
50 static void preMultipliedBGRAtoRGBA(const void* pixels, int pixelCount, unsigned char* output)
52 static const SkUnPreMultiply::Scale* scale = SkUnPreMultiply::GetScaleTable();
53 const SkPMColor* input = static_cast<const SkPMColor*>(pixels);
55 for (; pixelCount-- > 0; ++input) {
56 const unsigned alpha = SkGetPackedA32(*input);
57 if ((alpha != 0) && (alpha != 255)) {
58 *output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedR32(*input));
59 *output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedG32(*input));
60 *output++ = SkUnPreMultiply::ApplyScale(scale[alpha], SkGetPackedB32(*input));
63 *output++ = SkGetPackedR32(*input);
64 *output++ = SkGetPackedG32(*input);
65 *output++ = SkGetPackedB32(*input);
71 static bool encodePixels(const IntSize& inputSize, unsigned char* inputPixels,
72 bool premultiplied, Vector<unsigned char>* output)
74 IntSize imageSize(inputSize);
75 imageSize.clampNegativeToZero();
76 Vector<unsigned char> row;
78 png_struct* png = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
79 png_info* info = png_create_info_struct(png);
80 if (!png || !info || setjmp(png_jmpbuf(png))) {
81 png_destroy_write_struct(png ? &png : 0, info ? &info : 0);
85 // Optimize compression for speed.
86 // The parameters are the same as what libpng uses by default for RGB and RGBA images, except:
87 // - the zlib compression level is 3 instead of 6, to avoid the lazy Ziv-Lempel match searching;
88 // - the delta filter is 1 ("sub") instead of 5 ("all"), to reduce the filter computations.
89 // The zlib memory level (8) and strategy (Z_FILTERED) will be set inside libpng.
91 // Avoid the zlib strategies Z_HUFFMAN_ONLY or Z_RLE.
92 // Although they are the fastest for poorly-compressible images (e.g. photographs),
93 // they are very slow for highly-compressible images (e.g. text, drawings or business graphics).
94 png_set_compression_level(png, 3);
95 png_set_filter(png, PNG_FILTER_TYPE_BASE, PNG_FILTER_SUB);
97 png_set_write_fn(png, output, writeOutput, 0);
98 png_set_IHDR(png, info, imageSize.width(), imageSize.height(),
99 8, PNG_COLOR_TYPE_RGB_ALPHA, 0, 0, 0);
100 png_write_info(png, info);
102 unsigned char* pixels = inputPixels;
103 row.resize(imageSize.width() * sizeof(SkPMColor));
104 for (int y = 0; y < imageSize.height(); ++y) {
106 preMultipliedBGRAtoRGBA(pixels, imageSize.width(), row.data());
107 png_write_row(png, row.data());
109 png_write_row(png, pixels);
110 pixels += imageSize.width() * 4;
113 png_write_end(png, info);
114 png_destroy_write_struct(&png, &info);
118 bool PNGImageEncoder::encode(const SkBitmap& bitmap, Vector<unsigned char>* output)
120 if (bitmap.config() != SkBitmap::kARGB_8888_Config)
121 return false; // Only support ARGB 32 bpp skia bitmaps.
123 SkAutoLockPixels bitmapLock(bitmap);
124 IntSize imageSize(bitmap.width(), bitmap.height());
125 return encodePixels(imageSize, static_cast<unsigned char*>(bitmap.getPixels()), true, output);
128 bool PNGImageEncoder::encode(const ImageData& bitmap, Vector<unsigned char>* output)
130 return encodePixels(bitmap.size(), bitmap.data()->data()->data(), false, output);
133 } // namespace WebCore