A video showing the process of J index calculation

The video shows the method used for J index calculation in ImageJ.

J index is the percent similarity between a seed and a geometric model. The method departs from two images: one image contains the seed and the geometric model superimposed in white; the second image contains the same seed and the geometric model superimposed in black. With the former, Image J measures shared area between image and the model; while by the second, Image J measures total area.