I made a simple web UI[1] for generating images like this. It uses a Go library by Michael Fogleman[2] for all the heavy lifting—hat’s off to him.

For Bézier curves in particular, iteratively constraining the search around initial matches seems key to retaining detail (see the “rep” argument in Fogleman’s work), for example in the eyes of the Vermeer portrait in the OP.

[1]: https://github.com/kevin-hanselman/primitive-web-ui

[2]: https://github.com/fogleman/primitive