Hi,

so I hacked together a patch which compiles, but apparently it does
not do what I want:

> https://github.com/jchnkl/darktable/commit/f9da3a9bd21ab5673c0dad0083c6e40cb85c5d34

I suppose it's because the picker function isn't properly called or
executed.. as you can see I don't know anything about dt's internal
api :)

Could someone give me a hint on how to get all RGB values per pixel
for an image? :)

Thanks a lot,

  Jochen


On Fri, Aug 17, 2018 at 1:23 PM Jochen Keil <[email protected]> wrote:
>
> Hi Tobias,
>
> thanks for your answer and help!
>
> Now I have even more questions :)
>
> On Tue, Aug 14, 2018 at 2:53 PM Tobias Ellinghaus <[email protected]> wrote:
> [..]
> > > > I'm interested in writing an automatic white balance module or preset
> > > > for darktable, similar to rawtherapee's AWB mode. Briefly spoken, it
> > > > allows one to set a bias value for warmer / cooler tones and
> > > > calculates the color temperature using all pixels in the image (like
> > > > using the spot preset with a 100% area for the color picker).
> > > >
> > > > So far I kind of understand darktable's module interface, but I don't
> > > > understand how the color picker works.
> >
> > Since you are using the whole image anyway there is no need for using the
> > color picker. Just iterate over the image.
>
> That's why I wanted to learn about the color picker. I looked more
> closely at the `draw()` method and found that the picked color values
> are in `self->picked_color`. At least now I understand how the color
> picker works. :)
>
> > > > To my understanding, the color
> > > > picker can only function when in GUI mode?
> >
> > Yes. It's a way for the user to interact with dt.
> [..]
>
> That's a pity, because I was hoping for an easy implementation: Call
> the color picker without GUI interaction with an image area of 100%,
> then take the picked colors and just run it through the default
> algorithm.
>
> > > > 1) How can I get all the necessary information / color values from the
> > > > picture (color picker?)?
> >
> > Just look at the image. If you need the data from the full image you have to
> > use the preview pipe and sync the data to the other pipe. Some of the color
> > transfer iops should already do something like that.
>
> Can you give me a hint at what data structures to look at? There are
> several data structures called `dt_dev_pixelpipe_..` etc. and I can't
> figure out a) which one is the appropriate structure and b) how to get
> the color information. Maybe I can reuse some of the color picker
> code?
>
> > > > 2) How does the algorithm for calculating the white balance using a
> > > > bias look like?
> >
> > Maybe look at how RT is doing it.
>
> I'll do that. :)
>
> Cheers,
>
>   Jochen
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