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1 /* | 1 /* |
2 * Copyright (c) 2010, Google Inc. All rights reserved. | 2 * Copyright (c) 2010, Google Inc. All rights reserved. |
3 * | 3 * |
4 * Redistribution and use in source and binary forms, with or without | 4 * Redistribution and use in source and binary forms, with or without |
5 * modification, are permitted provided that the following conditions are | 5 * modification, are permitted provided that the following conditions are |
6 * met: | 6 * met: |
7 * | 7 * |
8 * * Redistributions of source code must retain the above copyright | 8 * * Redistributions of source code must retain the above copyright |
9 * notice, this list of conditions and the following disclaimer. | 9 * notice, this list of conditions and the following disclaimer. |
10 * * Redistributions in binary form must reproduce the above | 10 * * Redistributions in binary form must reproduce the above |
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53 return nullptr; | 53 return nullptr; |
54 | 54 |
55 png_struct* png = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0); | 55 png_struct* png = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0); |
56 png_info* info = png_create_info_struct(png); | 56 png_info* info = png_create_info_struct(png); |
57 if (!png || !info || setjmp(png_jmpbuf(png))) { | 57 if (!png || !info || setjmp(png_jmpbuf(png))) { |
58 png_destroy_write_struct(png ? &png : 0, info ? &info : 0); | 58 png_destroy_write_struct(png ? &png : 0, info ? &info : 0); |
59 return nullptr; | 59 return nullptr; |
60 } | 60 } |
61 | 61 |
62 // Optimize compression for speed. | 62 // Optimize compression for speed. |
63 // The parameters are the same as what libpng uses by default for RGB and RGBA
images, except: | 63 // The parameters are the same as what libpng uses by default for RGB and RGBA |
64 // The zlib compression level is set to 3 instead of 6, to avoid the lazy Ziv-
Lempel match searching. | 64 // images, except: |
| 65 // The zlib compression level is set to 3 instead of 6, to avoid the lazy |
| 66 // Ziv-Lempel match searching. |
65 png_set_compression_level(png, 3); | 67 png_set_compression_level(png, 3); |
66 | 68 |
67 // The zlib memory level is set to 8. This actually matches the default, we a
re just future-proofing. | 69 // The zlib memory level is set to 8. This actually matches the default, we |
| 70 // are just future-proofing. |
68 png_set_compression_mem_level(png, 8); | 71 png_set_compression_mem_level(png, 8); |
69 | 72 |
70 // The zlib strategy is set to Z_FILTERED, which does not match the default. | 73 // The zlib strategy is set to Z_FILTERED, which does not match the default. |
71 // Avoid the zlib strategies Z_HUFFMAN_ONLY or Z_RLE. | 74 // Avoid the zlib strategies Z_HUFFMAN_ONLY or Z_RLE. |
72 // Although they are the fastest for poorly-compressible images (e.g. photogra
phs), | 75 // Although they are the fastest for poorly-compressible images (e.g. |
73 // they are very slow for highly-compressible images (e.g. text, drawings or b
usiness graphics) | 76 // photographs), they are very slow for highly-compressible images (e.g. text, |
| 77 // drawings or business graphics) |
74 png_set_compression_strategy(png, Z_FILTERED); | 78 png_set_compression_strategy(png, Z_FILTERED); |
75 | 79 |
76 // The delta filter is PNG_FILTER_SUB instead of PNG_ALL_FILTERS, to reduce th
e filter computations. | 80 // The delta filter is PNG_FILTER_SUB instead of PNG_ALL_FILTERS, to reduce |
| 81 // the filter computations. |
77 png_set_filter(png, PNG_FILTER_TYPE_BASE, PNG_FILTER_SUB); | 82 png_set_filter(png, PNG_FILTER_TYPE_BASE, PNG_FILTER_SUB); |
78 | 83 |
79 png_set_write_fn(png, output, writeOutput, 0); | 84 png_set_write_fn(png, output, writeOutput, 0); |
80 png_set_IHDR(png, info, imageSize.width(), imageSize.height(), 8, | 85 png_set_IHDR(png, info, imageSize.width(), imageSize.height(), 8, |
81 PNG_COLOR_TYPE_RGB_ALPHA, 0, 0, 0); | 86 PNG_COLOR_TYPE_RGB_ALPHA, 0, 0, 0); |
82 png_write_info(png, info); | 87 png_write_info(png, info); |
83 | 88 |
84 return wrapUnique(new PNGImageEncoderState(png, info)); | 89 return wrapUnique(new PNGImageEncoderState(png, info)); |
85 } | 90 } |
86 | 91 |
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114 | 119 |
115 bool PNGImageEncoder::encode(const ImageDataBuffer& imageData, | 120 bool PNGImageEncoder::encode(const ImageDataBuffer& imageData, |
116 Vector<unsigned char>* output) { | 121 Vector<unsigned char>* output) { |
117 if (!imageData.pixels()) | 122 if (!imageData.pixels()) |
118 return false; | 123 return false; |
119 | 124 |
120 return encodePixels(imageData.size(), imageData.pixels(), output); | 125 return encodePixels(imageData.size(), imageData.pixels(), output); |
121 } | 126 } |
122 | 127 |
123 } // namespace blink | 128 } // namespace blink |
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