Methods for digitally noise averaging and illumination equalizing fingerprint images
First Claim
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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.
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Abstract
Methods for operating a programmable digital computer to enhance images of fingerprints represented by an array of pixel values. Methods for noise averaging, illumination equalizing, directional filtering, unhairing, curvature correcting, and scale correcting a fingerprint image are disclosed.
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Citations
7 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification