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Saturation flaw

PostPosted: Sun Jul 21, 2013 6:11 am
by SysOp
I think I found another bug...
When I adjust the saturation, some colours get messed up.
Below is an example JPEG compressed picture with a +25 saturation adjustment that exhibits the effect I am reffering to.
[picture file removed]
I hope this can be fixed.

Re: Saturation flaw

PostPosted: Mon Jul 22, 2013 12:01 pm
by Neosoft Support
It looks like what you're seeing is the distortion in the image caused by heavy JPEG compression. Photoshop's saturation effect will do the same thing - although at a higher setting due to differences in algorithms used by the two programs. If you try the same thing with a photograph not ruined by JPEG compression the results will be much better.

Re: Saturation flaw

PostPosted: Mon Jul 22, 2013 12:26 pm
by SysOp
Thank you for your reply, unfortunately you are wrong. Maybe I should not have mentioned it was a JPEG compressed picture. I just used the JPEG artifacts to exaggerate the effect. I can't reproduce the same effect by adjusting the saturation in any other application. If your Photoshop produces the same effect, it is also flawed.

Re: Saturation flaw

PostPosted: Tue Jul 23, 2013 8:15 pm
by Neosoft Support
The distortion in the JPEG image does greatly exaggerate the effect. My copy of Photoshop is quite old (I think it came free with a scanner or something), but it produces results similar to NeoPaint.

The saturation algorithm used for NeoPaint 5 is actually part of a library that we licensed from another company. I did look at the source code and it's a very simple algorithm - maybe too simple. It looks like there may be some wraparound when colors are saturated beyond a certain point, which shouldn't happen. I will make a note to discuss this with the company that makes the library and see if there are any alternative methods we can use in the future.