Hello,
This is my first post here.
I want to replicate the effect as seen in this sample:
Is it possible to create this effect using Gimp or G’MIC?
Or should a start by creating a line drawing from the photo and fill in the colors manually?
Thank you for your tips…
Hi and welcome!
I’m going to defer to some more graphical-oriented users like @lylejk for more current techniques, but there are quite a few filters in G’MIC that will likely get you pretty close to what you’re asking. Maybe the “Graphic Novel” filter in combo with some others?
Inkscape has a trace bitmap function with multiple options. File|Import the image, then Path|Trace Bitmap.
There are options for threshold values, edge detection, brightness cutoff, single path, multiple path options for brightness steps, colors, grays, smoothing, stacking scans, removing background.
It may take some playing around, but you can delete fills on the results if you like and widen, darken, lighten the drawn paths and adjust the transparency of the results for an overlay on the original. It also gives you excellent text tools for notations.
The result is a vector graphic. Probably worth playing with to see if it fits your needs.
If it doesn’t work as a path tracer it’s still an excellent choice for drawing your own graphics over an image.
Not sure of an easy flow to create this effect at the moment. Can try a blend of flamboyance illustration along with engrave (which I did; not showing) but it doesn’t really come close to this effect. 
I don’t think it’s an effect applied to the original image. I think it’s a hand drawing, probably from a Wacom type of tablet, drawing and painting on layers over the image in background.