How can I create a LUT on Linux with free and open source software?

Question

I use Linux for everything media production. I shoot RAW and process images with Darktable.

Now that I've started making videos too (4K ProRes), I need to apply a LUT to them in post. This requires importing a .cube file into Kdenlive. I know how to do that, but I don't know how to create a LUT.

Can I import a frame of video into Darktable, adjust the colors, and export a .cube file to import into Kdenlive to apply to the video?

Or are there other programs that will create a LUT on Linux? Can GIMP do it?

What Linux program can be used to create LUTs?

Answer 1

I was looking for that kind of software as well. Then I found the .cube specification.

I thought to myself ... an average programmer should be able to do it in a couple of days ... and then I did the job ;-)

It's called lutcraft, a command line tool written in python3.

You can find it on github:

https://github.com/EinExperte/lutcraft

Instruction:

1. Create a neutral png image

lutc lut-neutral.png

2. Manipulate the colors of the image

Do pixel-level color adjustments as desired.

Tools I suggest are darktable, gimp, flowblade or cinelerra. Any other program doing pixel-level imaging will do fine.

Then save the image. I assume you call the file lut-x.png.

3. Convert the image into a lookup table (.cube file)

lutc -i lut-x.png lut-x.cube

This will output a 3D lookup tabble corresponding to the file lut-x.cube

If you have any questions / suggestions / etc., feel free to comment or e-mail me.

Answer 2

You can try Photo Curves web app - since this is online tool - you can create 3D LUTs with it on Linux too - its free, no registration required:

https://photocurves.curvednebula.com/