Shells and Spheres: An n-Dimensional Framework for Medial-Based Image Segmentation

Figure 1

Each pixel is shown as a number indicating its integer distance from the central pixel. If we denote the central pixel as 𝐱, then pixels labeled 𝑛 are members of the set 𝐻_𝑛(𝐱). For example, the pixels labeled “3” (shown in bold) comprise the shell 𝐻₃(𝐱).