Tracing via broad brush strokes around the boundary

[ok37]

Option to trace by drawing the boundary pixels using a thick broad brush. The brush then draws an eroded edge along the boundary according to an intensity threshold or intensity gradient perhaps, while maintaining a 4 or 8 pixel neighbor with adjacent pixels. When edges are joined at the ends, the interior pixels are automatically filled in and assigned a cell index

[ok37]

The motivation here is 1) edge pixels, where variance between tracers is highest, are drawn automatically making overall results more reproducible and 2) this would speed up tracing if drawing a cell from scratch, especially for large structures