I don't think the OP really wants a hull and if then it wouldn't be convex. (Though stated otherwise)

It seems to be about tracing the - often concave - outline of a compact set of points - the pixel image of a county.

A hull is more general, it doesn't require that the enclosed points are connected.

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Wikisyntax for the Monastery

In reply to Re^2: Polygon Creation -- Request for Algorithm Suggestions by LanX
in thread Polygon Creation -- Request for Algorithm Suggestions by golux

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