GIMP - How to apply 3D LUT?

Hey

I need to apply a 3D LUT to a layer in GIMP, how do I do that?
Can it be done via ICC or HaldCLUT?

Possibly using G’MIC? Could you export the layer and apply the HaldCLUT directly using something like imagemagick? (Is the CLUT already in a HaldCLUT form?)

Yes, that is something that could be done in G’MIC, with the filter Film emulation / User-defined.
See screenshot below:

Here, I’ve chosen a HaldCLUT as a .png file, get from : http://gmic.eu/film_emulation/negative_old/clut/fuji_superia_100_+.png

but this should work with other CLUT files.

PS: I’ve also updated the filter today, to make it handle 16bits/channels CLUT files, so don’t forget to press the update button before using it :slight_smile:

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Does the CLUT have to be in a HaldCLUT form?

The 3D LUT can be in whatever format Photoshop can export it in. Thing is I don’t have Photoshop so I don’t know what formats those might be. If one of you, or someone reading this, does have access to PS, could you check? Then we’d know what our options are for using PS 3D LUTs in GIMP, G’MIC or other libre software.

@Morgan_Hardwood I have PS CS6 (Win 7, 64-bit). What would you like me to check?

@Claes there is an option to apply a 3D LUT, could you check two things?

  1. What file formats are accepted as input for 3D LUTs?
  2. What file formats can you save/export the 3D LUTs in?

@Morgan_Hardwood

I can use 3D LUTs in my PS CS6 version, and it looks like

  • 3DL
  • CUBE
  • CSP
  • look
    formats are allowed.

However, I cannot export 3D LUTs, exporting was introduced in the PS CC 2014 release. You will find more information here: https://helpx.adobe.com/photoshop/using/export-color-lookup-tables.html

OK?

Thanks @Claes!
I’m not familiar with those formats - if someone has sample files, please upload!

Ideally, GIMP should support applying a 3D LUT to a layer in whatever format is popular.
For now, we need to find and document the easiest way of being able to use a 3D LUT from PS (or from the world at large) in GIMP. That could mean converting one of those formats you listed into something GIMP/G’MIC can use (what can they use other than HaldCLUT? @David_Tschumperle?), or it could mean creating a HaldCLUT which has the same effect as those PS-compatible 3D LUTs have.

The only difficulty I found when dealing with HaldCLUTs is the gamma curve - it’s not always clear what to use.
Here http://rawpedia.rawtherapee.com/Film_Simulation I documented how to create a HaldCLUT using ImageMagick and then how to hack-create a DNG file for use as a HaldCLUT.

Step by step, we would need to:

  1. Get our hands on some 3D LUTs in 3DL, CUBE, CSP or ICC (is that “look”?) formats,
  2. Apply them to a publicly available test image.
    I recommend this one, just because it has a wide range of colors and I shot it so no licencing issues:
    http://rawtherapee.com/shared/test_images/colorspace_flowers.pef
    Ideally save that as a 16-bit 900px-wide TIFF (no need for a large image, keep it small), then apply those 3D LUTs in PS, and save the resulting images as 16-bit TIFFs.
  3. Apply the same 3D LUTs to a HaldCLUT identity file… or actually to two HaldCLUT files: one created using
    -colorspace sRGB, and the other using
    -colorspace RGB, as described in the RawPedia link, because we don’t know which one will work correctly.
  4. Upload the 3D LUTs + the original and processed photo TIFF + the original and processed HaldCLUT TIFFs
  5. We find out which combination leads to the same results, document it, ?, profit.

You can get a free Photoshop trial version from Adobe:
https://www.adobe.com/products/photoshop.html

@Morgan_Hardwood
Two clues found:
3dl file specification
http://download.autodesk.com/us/systemdocs/pdf/lustre_color_management_user_guide.pdf

Cube lut specification
http://wwwimages.adobe.com/content/dam/Adobe/en/products/speedgrade/cc/pdfs/cube-lut-specification-1.0.pdf

I started writing some LUT code for darktable a while ago and used these LUTs for testing: http://luts.iwltbap.com/#freeware. Those are CUBE files which are really easy to parse and process, the specs are here: http://wwwimages.adobe.com/content/dam/Adobe/en/products/speedgrade/cc/pdfs/cube-lut-specification-1.0.pdf.

If there is need for a simple tool that takes such a CUBE file and applies it to an image (or maybe even just creates a HaldCLUT) then ping me, I could probably turn my local test code into something useful.

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The Cube format seems to be a simple text file, should be easy to parse indeed. I’ll try maybe to add a G’MIC command to convert them into HaldCLUT.
By the way, when I see the size of a single CLUT file of 5Mb (zipped), ouch that hurts !
Good to know that we don’t use this format in G’MIC to store the 300+ HaldCLUT we have :slight_smile:

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I have recently being pointed to the OpenColorIO project, which is licensed under BSD and has support for a large number of LUT formats.

I’m still trying to understand all the functionalities offered by this library, and in particular how to insert it into ICC-based color-managed workflows, but it might be a good option to avoid coding the support for several LUT formats from scratch.

I found this but forgot to paste the link in the previous post:
http://opensource.mikrosimage.eu/ColorPipe-tools/LUTLab/LUT_to_LUT/

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I wouldn’t spend too much time on that. OpenColorIO is the movie industry’s competitor to an ICC workflow. In theory it might be possible to make the two work together, but in the real world it’s an either-or choice.

Being able to directly convert a format like Cube into HaldCLUT would be awesome!

Well, I’ve done a small test with one file found from the link @houz provided, and I’ve been able to import the CLUT data into G’MIC. That was a ‘manual’ attempt, so with head -n and tail -n to manipulate the .cube (text) file, but this worked. I’m pretty sure I can add at least a command that will be able to import some .cube files.

Ok, so here is a first attempt. Refresh your filters in the G’MIC plug-in for GIMP, and try to provide a .cube file to the Film Emulation / User-defined filter, like this :

And do not expect it to work :slight_smile:
This is something I’ve hacked in 20 minutes, so the chances it works for all .cube files is very low.
Of course, if it doesn’t work as expected, please tell me, eventually send me the corresponding .cube file for inspection.

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Salut! Tested with The Gimp 2.9.3 and g’mic 1.7.2.
Updated User-Defined Film emulation (got Latest update 06/11/2016). Tested a cube from PS6. Result:
Preview warning: Specified Hald-CLUT filename not found.