[Digikam-devel] local contrast plugin

[Julien Pontabry]

Julien Narboux a écrit :
> Mikolaj Machowski a écrit :
> > Hello,
> >
> > Looks like I've made injustice to new local contrast plugin in last DD.
> > Only later I noticed Gilles' screenshot
> >
> > http://www.flickr.com/photos/digikam/3771531595/in/pool-digikam-labs
> >
> > Knowing what it is about I was able to play with it a bit to some success
> > and it is great tool.
> >
> > But I have two problems with it:
> >
> > 1. Name: when you google for "local contrast" you will come with *many*
> > sites describing one of unsharp mask techniques while this tool is much
> > more similar in spirit to Highlighs/Shadows tools from other programs.
> > Even "Pseudo HDR" nick would be better description. From WhatsThis I
> > understand is sophisticated implementation of Contrast Mask technique
> > (BTW - I wonder if it would be possible to build smart sharpening based
> > on this plugin)
>
> It seems to me that this plugin does Highlights/Shadows recovery but
> taking into account the whole picture to preserve contrast.
> Maybe it could be called :
> "Local Highlights/Shadow recovery"
> "Local Tone Mapping"
> "Spatially Varying Tone Mapping"
>
> Look wikipedia for the definition of tone mapping :
>  http://en.wikipedia.org/wiki/Tone_mapping
>
> > 2. It is really hard to use. Only after I discovered connection with
> > Contrast Mask I was able to grok something but still struggle with
> > understanding what is what (eg. Stages?). Please, user documentation :)
>
> I guess stages are just several applications of the filter.
> You can find documentation on the web page of Nasca Octavian PAUL
> (http://zynaddsubfx.sourceforge.net/other/tonemapping/) upon which this
> plugin is based.
>
> I think before writing proper documentation, it would be nice to wonder
> if there is no better gui one can think of.
> I tested using only one stage and it was fine. Does anyone has examples
> which needs several "stages" to get a good result ?
>
> Julien Narboux
>
> ps: The plugin has still to be polished because 16bits and the progress
> bar do not work.
> Maybe preview could be faster using a downscaled image ? Julien, what do
> you think about that ?

I think we should first improve the plugin code to get it faster. I'm not sure 
using downscale is a good idea. See the real effect on a little part of the 
original image may be better, isn't it ?

Julien