Minutiae extraction by adaptive tracing the gray level ridge of the fingerprint image

This paper presents an improved approach of minutiae detection that adaptively traces the gray level ridge of the originals fingerprint image with piecewise linear lines of different length. While tracing the ridges, the fingerprint image is smoothed with an oriented smoothing filter only at selected pixels where smoothing is necessary. After tracing all the ridges, a piece-wise linear skeleton image is obtained. Each ridge in the skeleton is labeled with a number so that each minutiae is associated with one or two ridge numbers. The post-processing is based not only on the location relationship of the minutiae, but also the associated ridge relationship and the certainty level of the minutiae. The performance of this approach is objectively assessed by using two large fingerprint databases.