Elegant solutions for fingerprint image enhancement

A method of filtering a fingerprint image comprising the steps of:

• receiving an input fingerprint image;
• separating the input fingerprint image into plural, distinct segments, each segment having ridge-valley lines within a predetermined range of angles;
• directionally filtering each of said segments with a corresponding directional filter generally perpendicular to said predetermined range of angles of said segment;
• assembling said directionally filtered segments into a reassembled image;
• after said reassembling step, thresholding said fingerprint image by
• detecting all ridge-valley edge pixels,
• averaging pixel values of said detected edge pixels,
• setting each pixel in said reassembled image to foreground if said corresponding pixel value is greater than said average edge pixel value, and
• setting each pixel in said reassembled image to background if said corresponding pixel value is less than said average edge pixel value;
• after said thresholding step, watershed filling said foreground pixels including
• for each foreground pixel identifying other foreground pixels horizontally, vertically or diagonally adjacent, and
• replacing each foreground pixel with a background pixel if said identified foreground pixels are less in number than a predetermined number;
• and
• outputting said reassembled, thresholded and watershed filled image.