Table 1.

MSPA class descriptions (see Wickham et al. 2010).

Class	Description
Core	Foreground surrounded by foreground and greater than the user‐specified edge width from background
Edge	Foreground that separates core from background
Perforation	Foreground that separates core from interior areas of background
Bridge	Linearly oriented foreground that connects two disjunct core areas
Loop	Linearly oriented foreground that extends from core and connects back to the same core area (e.g. a handle)
Branch	Linearly oriented foreground that extends from core and terminates in background
Islet (patch)	Area of foreground that is too small to contain core