Outline Extraction
Outline extraction automatically traces the boundary of a prominent feature inside a region you select - it does not require manually tracing along an edge.
Creating an outline
Alt+drag a rectangle on the preview or a pop-out around the feature you want outlined. The tool automatically finds the brightest/most prominent connected region inside that rectangle (using an intensity threshold with morphological clean-up) and extracts its boundary as a contour overlay.
Because the segmentation is automatic, the result depends on how tightly the rectangle is drawn around the feature - a tighter selection around just the feature of interest generally gives a cleaner outline than a loose one that includes surrounding background.
Editing outlines
Right-click an existing outline for:
- Change color...
- Line width (several presets)
- Line style (solid, dashed, dotted, dense dash)
- Undo last outline - removes only the most recently added outline
- Clear outlines - removes every outline on the current view
Outline hit-testing is pixel-based and forgiving, so you don't need to click exactly on the thin contour line to select it.
Two different undo mechanisms
Undo last outline (in the right-click menu) is a dedicated, outline-only undo stack. The general Ctrl+Z canvas undo also covers outline add/clear/style actions, but as part of the same shared stack used by filters, crops, and other edits - so Ctrl+Z may undo something else first if you've made other changes since adding the outline.
Saving and restoring
Outline state is preserved through session save/load and virtual-copy workflows, the same as other canvas-side analysis state.