Basics of the Distance Transform Watershed algorithm. From left to right: sample image of touching DAPI stained cell nuclei from a confocal laser scanning microscope, binary mask calculated after filtering and thresholding input image, inverse of the distance transform applied to the binary mask (Chamfer distance map using normalized Chessknight weights and 32-bit output) and resulting labeled image after applying watershed to the inverse distance image using the binary mask (dynamic of 1 and 4-connectivity).