Right from the start of my studies I was learning how to convert photographs into vectorisations with Adobe Illustrator. Of course you could also do this automatically today but you'll only get a huge amount of tiny vetorised areas which isn't very useful. Especially when it comes e.g. to recoloring that graphic art. It's better to create the artwork manually which means recreating each area yourself.

Here you can see two examples that I created. One is with plain areas (a self portrait) and one using a gradient mesh to cause a three-dimensional look.

 

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