Patent ID: 7536038

Claim:
An arrangement for assessing the quality of skin print images, and particularly fingerprint images, characterized by a system for calculating gradients for pixels of a skin print image such that a gradient is calculated for each pixel of the skin print image, a mean value derived from the gradients of the pixels in each region of the skin print image, and a measure of quality from similarities in the mean values from region to region, wherein the system is arranged to enter the mean values in two directional matrices for x and y, to form scalar products of the directional matrices having matrices that are displaced horizontally, vertically and in the directions of both diagonals by one region, to sum, over all the regions of the skin print image, each of the products that are obtained by multiplying the matrices, and to form the quality measure by adding the sums together and dividing the scalar products of the directional matrices, said scalar products having been summed over all the regions, by themselves, wherein the quality measure is calculated using the following equation: Q = ( A x + A y + A xy + A yx ) 4 ⁢ A , where Q is the quality measure and A x , A y , A xy and A yx are the scalar products, wherein A x , A y , A xy , A yx and A are computed using the following equations: A x = ∑ k , l = 1 max - 1 ⁢ ⁢ 〈 [ ( g x ) k , l ( g y ) k , l ] , [ ( g x ) k + 1 , l ( g y ) k + 1 , l ] 〉 , ⁢ A y = ∑ k , l = 1 max - 1 ⁢ ⁢ 〈 [ ( g x ) k , l ( g y ) k , l ] , [ ( g x ) k , l + 1 ( g y ) k , l + 1 ] 〉 , ⁢ A xy = ∑ k , l = 1 max - 1 ⁢ ⁢ 〈 [ ( g x ) k , l ( g y ) k , l ] , [ ( g x ) k + 1 , l + 1 ( g y ) k + 1 , l + 1 ] 〉 , ⁢ A yx = ∑ k , l = 1 max - 1 ⁢ ⁢ 〈 [ ( g x ) k + 1 , l ( g y ) k + 1 , l ] , [ ( g x ) k , l + 1 ( g y ) k , l + 1 ] 〉 , ⁢ and A = ∑ k , l = 1 max ⁢ ⁢ 〈 [ ( g x ) k , l ( g y ) k , l ] , [ ( g x ) k , l ( g y ) k , l ] 〉 .