Wanted: channel remapping with implicit colorspace conversion

[Matthew Woehlke]

Cyrille Berger wrote:
>> [I]t seems like last
>> time I tried to load a .nef, Krita crashed and burned.
> 
> Well I just try, and it works fine.

I'll try again. Did you test uncompressed, or lossless-compressed? (For 
obvious reasons, I only use the latter; I usually get a size savings of 
around 40-45%.)

> There is still some processing since there 
> is no good solution for now to load non-processing raw file.
>  [re-arranging]
> 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.
>
> [1] http://wiki.koffice.org/index.php?title=Krita/Direct_RAW_Editing

Yes, I *seriously* doubt you would want to try to operate on bayer'd 
images. At "best", I'd treat it as a color space that must be converted 
before anything works, so you could a: save the exact raw data, and b: 
change the debayerisation algorithm, but everything would operate after 
conversion to a "normal" color space.

But I'm also unconvinced what the benefit would be. I'll stand by my 
question, how many knobs are there really to fiddle with in the 
debayerisation process? If there aren't many, or if the result of 
fiddling is negligible, then I don't see the benefit. (...And anyone 
that cares *that* much should know to not to delete the original raw.)

>> 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.

Other than being measured in E.V., is exposure really substantially 
different from brightness/contrast? It seems that Exposure+Contrast (as 
done by rawstudio) is just a simple 'Ax + B' mapping of the input data. 
So as long as you translate to a colorspace that doesn't lose precision 
too early in the pipe (I'm thinking, probably fp32), you should be able 
to emulate everything with curve mapping, no?

The obvious complication is that you might need multiple passes; the 
controls in rawstudio might not be presented in the order they are 
appplied, but if  they  are, rawstudio does brightness, then saturation, 
then hue, then contrast, then curves.

-- 
Matthew
Your eyes are weary from staring at the CRT. You feel sleepy. Notice how 
restful it is to watch the cursor blink. Close your eyes. The opinions 
stated above are yours. You cannot imagine why you ever felt otherwise.
   -- Unknown
(found at http://goldmark.org/jeff/stupid-disclaimers/fun.html)