Efficient Computation of the Euclidean Distance Transform

Thinning algorithms on binary images are used to generate skeletons that preserve the same connectivity structures as the objects in the original images. Two kinds of skeletons may be appropriate for 3D thinning algorithms: digital curves and digital surfaces. We propose two thinning algorithms on 3D (18, 6) binary images. One algorithm generates skeletons as digital curves and the other algorithm generates skeletons as digital surfaces. Both algorithms are 6-subiteration algorithms-in each iteration, they are applied alternatively to delete border voxels from each of the six directions, upper, lower, north, south, east, and west.