Semi-related to How to automatically draw the edge between two regions in GIMP?, is there any way in GIMP to stroke an area and create a line along areas of high contrast? I know that there are edge-finding filters, but they generally operate over an entire layer or selection thereof. I could probably draw a path and expand it into a selection over the area, then run the edge-finding, but it feels like this is something that can be done in a more automatic fashion.
The intent is basically to simplify tracing an object either to generate a line outline, or to trace the actual selection area for the purpose of isolating it from the background, similar to Contrast-based image outlining feature?, but not over the entire image.
To give an example, let's say I have this image of my hand over a reasonable neutral background:
If I run edge detect on it, I might get the following:
That provides Edge Detect over the entire image (and yes, I know I could probably do a better job of adjusting the contrast so that it gets the edge of my hand instead of that and all of my skin crenelations)
If I use Quick Mask, I can paint a selection area around the outline of my hand without being precise, run edge detect over that selection, and then delete the other parts.
Now obviously, I'm not good at adjusting the edge detection, although I've had some luck with using Threshold to get the edge back, and in this particular image, the shadow makes part of the hand not have a high contrast against the background, but I feel like there are a lot of cases where it would make sense to be able to just kind of paint the outline of something, and get the actual outline, probably with some adjustment of parameters so that you get that stark outline and minor differences around it.