try the Linux route,
extract this file as .gmic file and toss that under your $HOME/ folder.
see if that works.

...ummm there is nothing in the folder that I downloaded

Try using Notepad++ to open it.

If you're on a MAC files that start with a dot are hidden by default.
maybe this will help. http://www.macosxtips.co.uk/index_files/quickly-show-hidden-files.php

T - no such cool name - it's Richard Jo King Douglas

Mine would be TDDT...that's what my nickname was when we went camping..just TDDT.

Dalia,
did you get a chance to try that link i posted to see files that start with a dot?

I was just thinking of this script yesterday!

Thank you so much Tin for this nice filter. For any reason I missed it, so Thank you Pat for bringing it at my attention.
I had to try it just now.

You should try G'MIC->Testing->Garagecoder->Multi-threshold before running this script so you have more control over how the image turns out.

Thank you Tin. I'll practise it to get the right rate for each colour. Any hint for that?

With multi threshold i don't really have a master's technique. Usually i just move the lowest threshold to have black define most the image's detail, and then play with the rest of threshold to have them spread out so that it shows transition... I don't know if that's the best way i just like it to have black define most of the details.

Thank you Tin, just what I needed to know.