1.9.5 JPEG-li and Estimated quality

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vovka
Posts: 13
Joined: Fri Nov 30, 2007 10:32 pm

1.9.5 JPEG-li and Estimated quality

Post by vovka »

potentially dangerous behavior of 'Estimated quality'
for example:
i have a PNG file and i want to save it as JPEG
i select 'Save as' and in 'Options' I check 'Use JPEG-li' and set 'Quality' to 90
now I have a 185KB file, and 'Info' pane shows that 'Estimated quality' is only 57 (which is baffling)
i close the file
i reopen it
now I select 'Save as' and in 'Options' I uncheck 'Use JPEG-li' and check 'Use estimated quality'
now I have a 114KB file and 'Info' pane shows that 'Estimated quality' is also 57
but the quality of the file is now much worse because '57 quality of JPEG' and '57 quality of JPEG-li' are quite different qualities

i think XnView must somehow distinguish the files by their compression codecs and recalculate 'Estimated quality' accordingly
so that we do not accidentally downgrade our images
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xnview
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Re: 1.9.5 JPEG-li and Estimated quality

Post by xnview »

i have no way to check that a jpeg file was compressed in JPEG-li
Pierre.
vovka
Posts: 13
Joined: Fri Nov 30, 2007 10:32 pm

Re: 1.9.5 JPEG-li and Estimated quality

Post by vovka »

xnview wrote: Tue Nov 04, 2025 1:53 pm i have no way to check that a jpeg file was compressed in JPEG-li
thank you for the answer
i've noticed that ExifTools shows a different value for JPEG-li files
or it is not a reliable marker?
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