Wanted: channel remapping with implicit colorspace conversion

[Cyrille Berger]

On Tuesday 16 September 2008, Matthew Woehlke wrote:
> Cyrille Berger wrote:
> > On Monday 15 September 2008, Matthew Woehlke wrote:
> >> IIRC, a while back I'd talked about a way to transfer a color channel to
> >> an alpha channel via a node (i.e. such that it dynamically updates).
> >
> > A filter could do that, the alpha channel (and obviously other the other
> > channels) are available when filtering. That's basically what the Color
> > To Alpha filter does.
>
> Oh, do we have that already? I guess I haven't gotten krita to stay
> running long enough to poke around :-). (So can it perform an implicit
> colorspace conversion, so I can e.g. copy the Luma channel to Alpha from
> a layer that's RGB?)

No it can't, but one can write a filter that does that.

> >> Specifically, I want to be able to do this:
> >>
> >> -Start with two exposures of a raw*, 'e1' and 'e2'.
> >
> > For 2.0 (at least), the raw would have to be converted to one of the HDR
> > float color space.
>
> Well, obviously :-). Ability to import raw directly, with no processing
> except de-bayering and data-normalization (i.e. converting from the
> sensor's 12- or 14-bit to fp32) is preferred, but as I mentioned, I
> could also convert them to 16-bit TIF in rawstudio. (Of course, I'll get
> a better result with direct-import because it will preserve the HDR
> information for later blending; a major plus!) But it seems like last
> time I tried to load a .nef, Krita crashed and burned.

Well I just try, and it works fine. There is still some processing since there 
is no good solution for now to load non-processing raw file.

> Krita is part of the beta, yes? If so, I'll raise my expectations and
> start filing bugs rather than assuming "it's not ready yet" like I've
> been doing.

It has been ready for bugs report for a while ;)

> When you say "for 2.0", what other options would there be? Is de-bayer
> really finicky enough that we need to preserve the original bayer'd data
> and allow the de-bayer algorithm to be tweaked like any other filter layer?

What I said is that there is no exposure filter, so the only way to adjust 
exposure is through the overview filter which only work for HDR color spaces.

In Krita debayerisation is an other story, you can see my thoughts on the 
subject in [1]. But, now I am not so sure that it is really a good idea. For 
one thing, debayerisation is a linear process, and for an other, quiet a few 
important operation need the full RGB triplet to be remotely useful.

> >> Bonus points if Krita can do everything rawstudio can... which I *think*
> >> it can, except it seems raw import wasn't stable last I tried,
> >
> > /me looks around for the bugs reports ;) I only tried with nef and it
> > works fine for me.
>
> Curious, I'll try to look again as soon as I get a chance, but IIRC it
> wasn't working last I tried. (I have a D300, so, also .nef.)
>
> Hmm... I wonder if it's getting bit by a dcraw bug. I'm using a hacked
> rawstudio b/c it would overrun the dcraw buffer by 8 bytes, which a:
> made importing the camera white balance not work, and b: destroyed the
> heap causing it to crash as soon as I tried to load a second image. I'm
> suspicious that this is actually a dcraw bug (making the buffer 16 bytes
> larger fixed it for rawstudio), and so I wonder if dcraw is misreporting
> the data size, which might be killing krita as well.

I tried with one of the D300 RAW sample and it works for me. But if you are 
hit by a bug in dcraw, there isn't much we can do about it ;)

> I'd like to get digikam to where it can both manage albums AND do the
> processing work I currently do in rawstudio. Right now digikam doesn't
> seem to work, period (I can't get it to show any pictures, ever, so I
> don't even know what it does).
It's not related to that list, but I heard that the solution is to clear the 
database and to start a new one. It seems the import from old database to the 
new one is broken.

[1] http://wiki.koffice.org/index.php?title=Krita/Direct_RAW_Editing
-- 
Cyrille Berger