Once you have a good contrast on your b-and-w pic, use the selection tool, then convert the selection to a path. The path can then be cleaned/prettied up and exported as a vector file which can be scaled to any size.

RosemaryR
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"This...this is magnificent!"
"Oh, yeah. Ooooo. Aaaaah. That's how it starts.
Then, later, there's ...running. And....screaming."