terrible jpg quality after resize

Discussions on NConvert - the command line tool for image conversion and manipulation

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EuM_Expert
Posts: 20
Joined: Mon Jul 23, 2012 1:54 pm

terrible jpg quality after resize

Post by EuM_Expert »

Hi Forum,

I use nconvert.exe version 7.110 to resize (compress) jpg files in a folder to save on size.
The result is terrible, pictures very "pixely" and definitely a large diversion from the originals.
i played around with the parameters, and either the quality remains acceptable but at a large file size (1MB per file), or the result is unusable.

Here is the command line.

%csNCONVERT% -keepfiledate -overwrite -ratio -rtype lanczos -rflag decr -rflag orient -resize longest 1400 -autolevels -autocontrast -normalize %csIMAGES%

I used XnConvert (the graphic windows program) and the results are similar to the command line tool, i.e. disappointing.

Any comments would be great. Thanks.
cday
XnThusiast
Posts: 3295
Joined: Sun Apr 29, 2012 9:45 am
Location: Cheltenham, U.K.

Re: terrible jpg quality after resize

Post by cday »

Are you able to provide an example source file, and if possible also the corresponding resulting file?

You haven't specified a JPEG save quality term, but as the default is quite high (75 or 80, I think) that shouldn't be an issue.

Have you tried removing as many terms as possible to see if you can obtain satisfactory quality with only essential terms?

Edit:

The fact that XnConvert provides a preview of the effect of the actions applied, and that individual actions can be temporarily deselected, should in fact make it reasonably easy to identify where the quality issue is being introduced: it is possible if necessary to zoom into the preview image, and it should also be possible to determine whether the issue is present before the final image is saved.