[ptx] Display gamma (was:Vignetting correction in nona)

[Kai-Uwe Behrmann]

I shortened your message a bit.

Am 03.01.06, 17:47 +0100 schrieb Pablo d'Angelo:

> Actually since hugin is not really a photo editor it is not terribly important
> that the color display is 100% accurate, but if it can be done easily (and
> without performance issues), why not.

There are performance issues. Lcms is in this regard not like photoshop.

> I guess it would mean that the displayed images need to be transformed with
> lcms while loading. Shouldn't be too hard to add.

I backported this feature in CinePaint. For big images (~50MB) it takes 
too long to load. I get easily a hugin projects with 1GB and more. The 
update should allways be for the pixels actually displayed. Maybe a switch 
for zooming in.

> I'm not an expert in color management, but for stuff like the vignetting
> correction it would be great to work with a linear (intensity proportional to
> gray values) image.
> It would be nice if the image could be transformed into a linear colorspace
> for this. I'm not sure if this can be done if images with good input profiles
> are given.

In 16-bit less an issue.

regards
Kai-Uwe Behrmann
                                + development for color management 
                                + imaging / panoramas
                                + email: ku.b at gmx.de
                                + http://www.behrmann.name