Patent attributes
A method includes: normalizing intensities at each pixel in a fingerprint slap scan image such that variations of pixel intensities between fingerprint ridges and valleys are regularized; subsequently dividing the fingerprint slap scan image into blocks of pixels; for each block of pixels, estimating a spatial separation between adjacent fingerprint ridges as well as a ridge orientation for each fingerprint ridge within the particular block of pixels; calculating a distortion map for the various blocks by projecting, according to the estimated ridge orientation for each fingerprint ridge, an adjustment to the estimated spatial separation that is based on a difference between the estimated spatial separation and a target spatial separation; and warping the fingerprint slap scan image to compensate for the calculated distortion map such that the fingerprint ridges in the warped fingerprint slap scan image are scaled to compensate for local variations of adjustments in the calculated distortion map.
