[Kdenlive-devel] Color correction tools: How and where to implement them?

[Simon A. Eugster]

Hi Hugh,

> In fact Kdenlive already has :
> * levels (interface isn't great, but it does the job allright)
> * Curves (with a new curve widget from Krita if I'm not mistaken)
> * 3-way color correction (actually never used it seriously, not sure how
> usefull it is)

I didn't see levels and 3-way CC (installed frei0r the wrong way, so the 
plugins were not sorted).

What still needs to be improved:
* Curves is not really useful at the moment because of the
   chosen interpolation method. For example, this curve is
   impossible for now:
   http://granjow.net/uploads/kdenlive/gimp-curves.png
   Also it is limited to only 3 points, which is not enough
   for earnest color correction.
* 3-Way color correction works basically quite well,
   but the usability is terrible.
   If you want to change the blacks, you have to rise the black
   value to see colors in the color picker, and at the end make
   it nearly black again. Would be much better to just chose a
   color and not having to worry about black.
   Also is it not very convenient not to have a live preview.
* White balance: You cannot click into a monitor to pick a
   neutral color from there.
   You should also be able to change the color temperature
   as this also belongs to white balance.

> The way Curves was implemented (by using a frei0r plugin and adding a
> widget from Krita) seems to me like being the easiest and most efficient
> way...

But not for the color displays?
I would want to have separate widgets for each color display, for being 
able to look at multiple color displays at the same time. Also, using 
frei0r there would make the displays depend on the video size.

Simon

>
> Please correct me if I'm wrong.
>
> Cheers,
> Hugh
>
>
> 2010/7/7 Simon Eugster <simon.eu <http://simon.eu>@gmail.com
> <http://gmail.com>>
>
>     Hi lists, hi Dan,
>
>     As kdenlive lacks basic color information and correction tools like:
>     Information:
>     * Levels
>     * RGB parade etc
>     * Vectorscope/Waveform
>     Correction:
>     * Curves
>     * Values
>     * Others known from GIMP
>     * 3-way color correction (blacks, mids, whites)
>     I wanted to ask two things.
>
>
>     First thing is: We have been discussing about using Gimp, GEGL, and
>     ShowFoto.
>     http://sourceforge.net/mailarchive/forum.php?thread_name=200907081050.55569.kamikazow%40web.de&forum_name=kdenlive-devel
>     <http://sourceforge.net/mailarchive/forum.php?thread_name=200907081050.55569.kamikazow%40web.de&forum_name=kdenlive-devel>
>     http://www.kdenlive.org/forum/call-integrate-gegl-library-mlt-plugin
>     http://www.kdenlive.org/forum/studying-digikam-color-and-light-tools
>     What is the current status?
>     It is not long ago yet and we have all been busy, so maybe nothing has
>     changed since.
>     And about speed of GEGL etc.: My opinion: Better slow color correction
>     than no color correction at all.
>
>
>     Second thing: The color information tools. As far as I know most of
>     them would have to be programmed first. But how? I'm currently trying
>     to figure out how to calculate a vectorscope display (it seems that
>     everyone in the web knows how to do it, because there are plugins for
>     every possible tool, but they are always in binary form, and I have
>     been searching for hours for a formula and haven't found anything).
>     Now I could just make it a frei0r effect. But as a) frei0r seems to be
>     dead and b) a vectorscope is not used as effect that should be visible
>     in the rendered video, I want to ask you how this would best be
>     implemented. Ideally such that it is reusable by other programs.
>
>     The point is also, I would like to do it interactively. Means, if I
>     e.g. have a levels display[1] I would like to be able to select the
>     lower 25 % of the curve (all dark pixels) and have them highlighted in
>     the kdenlive project monitor. So I guess neither frei0r nor MLT would
>     be suitable for that at the moment? (I don't know MLT yet, and frei0r
>     only partially) Could MLT probably be extended this way, or is this
>     not intended?
>
>
>     Simon
>
>     [1] http://docs.gimp.org/en/gimp-tool-levels.html
>
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