Igor Escobar igorescobar
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igorescobar
/ getJpegQuality.js
Created
May 15, 2020 18:35
— forked from FranckFreiburger/getJpegQuality.js
pure JavaScript jpeg quality value recover
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| // javascript jpeg decoder: https://github.com/eugeneware/jpeg-js/blob/79c4c7ea876d2e7b46981a563fcc4ae8f9e19849/lib/decoder.js | |
| // Determine the JPEG compression quality from the quantization tables: https://github.com/ImageMagick/ImageMagick/blob/59f28acff016f6ae5e8b7e6300bcdf97e94affc9/coders/jpeg.c#L879 | |
| // JPEG File Layout and Format: http://vip.sugovica.hu/Sardi/kepnezo/JPEG%20File%20Layout%20and%20Format.htm | |
| // jpeg constants: https://github.com/LuaDist/libjpeg/blob/6c0fcb8ddee365e7abc4d332662b06900612e923/jpeglib.h#L45 | |
| function getQuantizationTables(data) { | |
| var quantizationTables = [] | |
| var dctZigZag = new Int32Array([ |
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