How to uncompress gmic_film_cluts.gmz ?

Software G'MIC
1

Hi, with Jean-Paul Gauche (I met him on the darktabke.fr forum), we are trying to convert various film emulations into darktabkle styles. We kniow it won’t be 100% accurate but we try our best to improve the process.

We can convert styles expressed as HaldCLUTs PNGs a s those used in Rawtherapee. We’d like to convert G’MIC film emulations and styles, but all we can find is the gmic_film_cluts.gmz file (https://github.com/dtschump/gmic/blob/master/resources/gmic_film_cluts.gmz). How can I uncompress gmic_film_cluts.gmz ? Will it produce PNG files ?

Best, Pierre.

2

CLUTs in G’MIC are represented in a compressed way (sparse colored point cloud in the RGB cube), so each CLUT need to be decompressed before saving it to a .png file.
The following G’MIC command does the job:

cluts2png :
  v - i http://gmic.eu/gmic_film_cluts.gmz
  N=$! repeat $N l[$<] n={n}
    v + e[] "  > Decompress CLUT '"$n"' ["{1+$>}/$N"]" v -
    decompress_clut 64
    r 512,512,1,3,-1 w -1,-1,0,$n
    o $n.png
  endl done v +

It outputs 359 .png files (resolution 512x512), corresponding to all the CLUTs available in G’MIC.
Here is the link to the zip file containing all these PNGs : http://gmic.eu/gmic_film_cluts_png.zip

2 Likes
3

Thank you so much !!! Just one question : what does the “64” denote in “decompress_clut 64” ?

4

That is the resolution of the CLUT along the R,G and B axes.
64 is a good choice because 64^3 = 512^2, which means the resulting 3D CLUT can be easily converted to a 512x512 2D png image.
Choosing 16 is also possible (as 16^3 = 64^2), but it is maybe a quite low resolution for storing all the variations happening in some CLUTs.
Other choices of resolutions would lead to incompatible sizes when converting to a 2d image.

5

Hello, thanks for all this information that will be useful in making dtStyle for darktable. For now, I was doing it using the proposed method: https://www.youtube.com/watch?time_continue=3&v=m_cLCL5PJk4
There was a post: Howto use the new CLUT module
but the dtStyle I was doing wasn’t very satisfying.
Best regards.

1 Like
6

RawTherapee also uses a bunch of the same film simulations (though I think G’MIC has more). You can download those files from RawPedia.

7

I really should redo that video with a modern version of darktable since I made it when the LUT module in darktable was still in development (which is now years ago).

8

Indeed, we have used the proposed HaldCLUT. I have been following Pat Davis’ works for a long time and I tried them with darktable, a Git branch allowed to use them. Conversions to dtStyle give quite variable results. We are looking for a method that gives comparable RAW treatments in darktable and RawTherapee before applying styles.

9

Yes @dutch_wolf, you made an.cht file which allowed me to follow your tuto and to be able to make an.pdf in French. The method @temperdu has developed is different. We talk about it on: https://darktable.fr/forum/showthread.php?tid=1841&highlight=dtstyles
This forum is in English but you should be able to follow with the online translation as I do to follow you here. Best regards.

1 Like
10

Is there way to convert those to OBS Studio? I tried the PNG’s but OBS produce images that resemble EGA graphics of the early 90s. :wink:

11

What type of LUT does OBS support?

12

I have no clue. Couldn’t find any documentation on it. The OBS Wiki only has a title for coloring, but no text. Found a few articles that showed how one can generate the LUT’S with Photoshop but that didn’t really help either. Apparently it is some type of Haldclut, but the PNG’s of gmic aren’t usable with OBS Studio.

13

You can get the same LUTs from RawTherapee here: http://rawtherapee.com/shared/HaldCLUT.zip