Search found 5 matches

by elmo
2019-05-24T01:27:14-07:00
Forum: Bugs
Topic: Custom Quantization Tables using defineValue
Replies: 1
Views: 8891

Re: Custom Quantization Tables using defineValue

You need to set the jpeg output quality to 50 otherwise the library scales the quantization tables. I've posted about this in a different thread.
by elmo
2019-05-15T04:00:52-07:00
Forum: Bugs
Topic: -define jpeg:q-table not respected
Replies: 2
Views: 2866

Re: -define jpeg:q-table not respected

The solution is to use the ImageMagick flag -quality 50 . The jpeg library converts this to a value of 100 via the function jpeg_quality_scaling() . This value of 100 will be passed to jpeg_add_quant_table() , negating the effect of the scaling (see the scaling function I posted earlier). I have not...
by elmo
2019-05-15T02:10:04-07:00
Forum: Bugs
Topic: -define jpeg:q-table not respected
Replies: 2
Views: 2866

Re: -define jpeg:q-table not respected

I've tracked down the problem: -define jpeg-qtable uses the standard jpeg library's jpeg_add_quant_table () function which scales the provided quantization table by the jpeg quality using the function: q value = round(provided_table_value * scale / 100). There is no provision to define a verbatim qu...
by elmo
2019-05-12T14:15:34-07:00
Forum: Bugs
Topic: -define jpeg:q-table not respected
Replies: 2
Views: 2866

-define jpeg:q-table not respected

Version: ImageMagick 6.9.7-4 Q16 x86_64 20170114 http://www.imagemagick.org Copyright: © 1999-2017 ImageMagick Studio LLC License: http://www.imagemagick.org/script/license.php Features: Cipher DPC Modules OpenMP Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl l...
by elmo
2019-05-12T14:08:03-07:00
Forum: Developers
Topic: SET DQT via -define jpeg:q-table
Replies: 1
Views: 5226

Re: SET DQT via -define jpeg:q-table

I'm having the same problem. Any luck?