Representative shape descriptors used in image processing
| Image shape descriptor . | Expression . | Range . |
|---|---|---|
| Form factor based on circle | FF* = 4πA/P2 | (0,1] |
| Form factor based on square | FF** = 16A/P2 | (0,1] |
| Roundness | R= 4A/(πDmax) | (0,1] |
| Aspect ratio | Ar = Dmax/Dmin | [1, + ∞] |
| Elongation | E=Lmax/Lmin | [1, + ∞] |
| Convexity index | CI=Pconvex/P | (0,1] |
| Solidity index | SI=A/Aconvex | (0,1] |
| Compactness | C= ((4/π)A)0.5 | (0,1/π] |
| Image shape descriptor . | Expression . | Range . |
|---|---|---|
| Form factor based on circle | FF* = 4πA/P2 | (0,1] |
| Form factor based on square | FF** = 16A/P2 | (0,1] |
| Roundness | R= 4A/(πDmax) | (0,1] |
| Aspect ratio | Ar = Dmax/Dmin | [1, + ∞] |
| Elongation | E=Lmax/Lmin | [1, + ∞] |
| Convexity index | CI=Pconvex/P | (0,1] |
| Solidity index | SI=A/Aconvex | (0,1] |
| Compactness | C= ((4/π)A)0.5 | (0,1/π] |
Note: Dmax: maximum diameter, Dmin: minimum diameter, Lmax, length of the major axis, Lmin: length of the minor axis; L: main stream length; Pconvex: convex hull perimeter, Aconvex: convex hull area (modified from Russ (2002) and Jiao et al. (2012)).