With a friend I saw a big portrait image that has a good likening of the person when you look at it from a distance. But when you get nearer you see that the portrait is composed with a huge number of small portraits of different persons, all tiled side by side: so the portrait has "big pixels that are in itself small images".

I would like to make such a portrait. First using only one portrait as small image to compose a bigger tiled image of the same portrait. Later also using different portraits.

Can someone tell me what program (Inkscape, Gimp, Scribus) I can use for this and If there is a manual for the procedure. I could not find it on the internet, but didn't know well how to describe this procedure in a few words :-) .

Joop