The preprocessing of palmprint includes the palmprint segmentation and the palmprint image enhancement. According to the shortcomings of the existing preprocessing methods

in this paper

we propose a new preprocessing method of palmprint. The method uses the outside boundary of a palm as the reference line to align a palmprint. It also includes the usage of the center of the largest inscribed circle as the origin of the coordination system of palmprint and extracts the center part of the palmprint

which complete the palmprint segmentation. In addition

to enhance the contrast of palm images

this method introduces the fuzzy set theory into the unsharp masking scheme and replaces a Laplacian filter with steerable filters to extract the high frequency components. The experiment results demonstrate the method can not only extract the center part of palmprint

even under the circumstance of adducting the all of fingers

but also enhance the contrast of principle lines and wrinkles synchronously.