Patent Document ID: 4811414
Application ID: 07020331
Patent Status: 1

Claim One:
1. A method for operating programmable computing means to illumination equalize input pixel values of an array of input pixel values characteristic of a fingerprint image so as to produce an illumination equalized array of pixel values characteristic of an illumination equalized image, including: receiving an array of input pixel values characteristic of a fingerprint image; selecting equalizing subarrays of input pixel values, each including an input pixel value to be illumination equalized; generating subarray average values as a function of the pixel values within the equalizing subarrays; subtracting the subarray average values from the corresponding pixel values being equalized to generate pixel difference values; adding a predetermined constant to the pixel difference values to generate intermediate illumination equalized pixel values; setting the illumination equalized pixel values equal to a predetermined minimum pixel value if the corresponding intermediate illumination equalized pixel values are less than the minimum pixel value; setting the illumination equalized pixel values equal to the corresponding intermediate illumination equalized pixel values if the corresponding intermediate illumination equalized pixel values are greater than or equal to the minimum pixel value, and less than or equal to a predetermined maximum pixel value; setting the illumination equalized pixel values equal to the maximum pixel value if the corresponding intermediate illumination equalized pixel values are greater than the maximum pixel value; and storing the illumination equalized pixel values as an array of illumination equalized pixel values characteristic of the fingerprint image.