Fig. 12
From: Stopping criterion for linear anisotropic image diffusion: a fingerprint image enhancement case
Spatial Entropy for a real fingerprint image under linear anisotropic diffusion process. a displays spatial entropy graph of an acquired digital fingerprint. b depicts the entropy-change graph with one clear peak. the peak goes well with half-width of the average ridge present in fingerprint image. The diffused image obtained by peak of entropy-change is depicted in (c). While the image shown in (d) is the image we will ultimately get if we let the diffusion go on for a long enough diffusion time