How to create HaldCLUT from difference between two images

Hey @David_Tschumperle

Sometimes one would like to be able to create a HaldCLUT of processing done by some hardware or software which does not permit you to pass through it a HaldCLUT identity image. One solution would be to photograph the identity image (or some color target with patches), process that raw photo in said hardware/software and save as a separate file, and then use the before/after non-raw images to create the HaldCLUT.

For example, to create a HaldCLUT of a camera’s “Portrait creative style”, you could shoot some target, process the raw photo in-camera to apply the style, and then end up with two JPEGs - a reference image and the styled image. Now the difference must be mapped so that a HaldCLUT can be created.

Could G’MIC help with that?

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Filter CLUT from After/Before Layers is not enough ?


Yes, that should do it - thanks @David_Tschumperle!

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Ha glad to see this may be useful, let us know if you succeed in doing something nice with this filter!

Cross posting from RawTherapee forum where this thread was linked.

Interesting and tried that but options are creating either an eight column 512 x 512 png or a sixteen column 4096 x 4096 png neither of which showed up in RT where all Hald CLUT png files are twelve column 1728 x 1728. What am I missing :worried:


@mannikon Can you upload the 512x512 png to and post a link here? I will have a look then…

Will do. Not straight away, middle of processing something. Thanks!

@heckflosse -


It works just fine here.
The result is somewhat peculiar, though… But it shows up in RT and affects the image.

I can confirm what @Claes wrote

Did you restart RT after installing the HaldCLUT in it’s folder?

@Claes @heckflosse - hmm. Puzzled now.

@sguyader - I did the other day, forgot to check it today (I had deleted the files).
Will check now … doh! simple mistake! my new folder had to be read-only, works now. Still puzzled about different resolutions but can experiment now! Thanks for bearing with me :kissing_heart:

(will update the RT thread)