editor - IJG library or Windows photo viewer DQT generation -

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the question is: how windows photo viewer generates dq (discrete quantization) tables? and/or how editor or application uses ijg library generates dq tables? i'm trying find out algorithm of recomputing tables when image resaved , parameters of computes them.

the ijg library uses baseline set of quantization tables using sample 1 in jpeg standard (or @ least used to). uses "quality" parameter scale values in tables. off top of head, quality setting 75 uses unmodified table. quality values higher baseline scale values smaller. lower quality values scale them larger.


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