In an image where grey values plotted as height resemble a mountain landscape, I find the summit. In an attempt to isolate the peak, from that location, I want to lower a horizontal (=same grey value) loop of rope around the peak, until it lowering is prevented by a saddlepoint between the summit and a nearby lower peak. Then I can cut out the peak for further analysis.
Just Enlarging… the ROI by 1 wouldn’t work because the steeple is not a perfect vertical cone and thus the loop (ROI) wouldn’t remain horizontal. Not every grey value (height) is available on the slope around the summit, so the solution must be robust enough to allow skipping grey values.
Also the peak is not perfectly round, so convex parts of the ROI may exist. Watershed-ding demands a binary image and because the adjacent peak may be much lower, thresholding is not straightforward.
Flood fill wouldn’t necessarily find 8-connected neighbouring grey values.
Is there a nifty trick or a built-in command for this region growing based on monotonically descending grey value?