Figure 1.

Landmarks are detected by measuring the internal angles around the periphery of the nuclei. (A) The ZR method is based on approximating the true curved shape as a lower resolution polygon with fixed side lengths. The same underlying curve can be encoded multiple ways (a–e) depending on where the vertices of the polygon fall in relation to the underlying shape. For example, the tip is detected well in (a), but not the tail socket; the reverse is true in (d). No individual encoding captures all nuclear features. (B) We measure the angle at every individual pixel around the original shape. This method combines the data from every possible polygonal approximation into a single unified trace, from which landmark features can be detected. (C) Features are marked on a nucleus: 1—tip; 2—under-hook concavity; 3—vertical; 4—ventral angle; 5—tail socket; 6—caudal bulge; 7—caudal base; 8—dorsal angle; 9–11—acrosomal curve. (D) Definitions of key measured parameters used in the software from Table 2. The nucleus center-of-mass is a blue dot. Automatic vertical orientation is used to determine bounding dimensions.