Fig. 10From: Stopping criterion for linear anisotropic image diffusion: a fingerprint image enhancement caseNon-uniform illumination correction. a shows an acquired digital fingerprint. b depicts the estimated illumination surface, clearly showing non-uniform background lighting conditions. c is an output result after passing the image through homomorphic filtering operation and then linearly stretched. We observe that illumination has been corrected with clear ridge/valley structureBack to article page