[Digikam-devel] Adjusting filters to be deterministic

[Aditya Bhatt]

ALGLIB (GPLv2) might be worth a look...

On Thu, Jun 17, 2010 at 8:08 PM, Gilles Caulier <caulier.gilles at gmail.com>wrote:

> 2010/6/17 Marcel Wiesweg <marcel.wiesweg at gmx.de>:
> >
> >> JulienN raised a good idea in comments under my blogpost. Rewrite the
> >> filters to be deterministic and thus fully reproducible. This would help
> a
> >> lot for non-destruct. editng. I would go with leaving the random init
> part,
> >> but alter the filters in such way, that we can store the output values
> and
> >> reuse it later with those exact same values to get an exact same output.
> >>
> >> The benefits would be quite big for NDE as now the concept is such, that
> >> with using any non-reproducible filter, new file must be created to
> >> preserve this exact output and also, any edit you did prior that will be
> >> unremovable without losing this output. Example: you use brightness,
> >> contrast and raindrops and then some other filters. Now you see that the
> >> initial brightness is not very good so you want to change/remove it. But
> >> if you do so, you must reapply all the filters in the stack which are
> >> after
> >> brightness. But since you can't reapply the raindrops, you need to lose
> >> this and that means you will lose any other edits you did after
> raindrops
> >> too.
> >>
> >> What do you think? Would it be possible to alter all the filters so they
> >> could be reproduced to get the exact same output? I don't have very good
> >> code knowledge of them.
> >
> > Yes, it's a very interesting point.
> >
> > 1) Which filters are affected? A search for rand reveals:
> > - BlurFX
> > - DistortionFX
> > - Filmgrain
> > - Raindrop
> > - localcontrast
> > - in the CImg library
> >
> > I would separate out one group of filters: Those depending on very
> complex,
> > possibly externally develop algorithms like CImg. For these, the
> algorithm can
> > change with library updates, we dont have full control anyway.
>
> CImg is included in digiKam. So the problem can be wrap around.
>
> But... last CImg do not include GreyStoration algoritm now. a new
> library have been developped and is named GMic... I already take a
> look into this lib, and i lost. It's difficult to use with digiKam
>
>
> > I am not sure which other plugins fall into this group; localcontrast?
> Gilles
> > knows more about that.
>
> I'm not sure to understand. Why localcontrast fall into this group. it
> just a color correction tool as BCG, or HSL...
>
> Gilles
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-- 
Aditya Bhatt
Blog : http://adityabhatt.wordpress.com
Bitbucket: http://bitbucket.org/aditya_bhatt
Face Recognition Library : http://libface.sourceforge.net
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