ANSI/NIST-ITL 1-2011 - NIST Visual Image Processing Group ...

ANSI/NIST-ITL 1-2011Data Format for the Interchange of Biometric and Forensic Information13.5 Fields 9.031 – 9.125: Registered vendor minutiae fieldsSee Table 12 for the vendor names. The vendors define these fields.13.6 Fields 9.126 – 9.150: M1-378 / ISO 19794-2 Minutia dataThe following method shall be used for determining placement (location andangular direction) of individual minutia when using this data block.The position or location of a minutia representing a ridge ending shall be thepoint of forking of the medial skeleton of the valley area immediately in front ofthe ridge ending. If the three legs of the valley area were thinned down to asingle-pixel-wide skeleton, the point of the intersection is the location of theminutia. Similarly, the location of the minutia for a bifurcation shall be the point offorking of the medial skeleton of the ridge. If the three legs of the ridge wereeach thinned down to a single-pixel-wide skeleton, the point where the three legsintersect is the location of the minutia.After all ridge endings have been converted to bifurcations, all of the minutiae ofthe fingerprint image are represented as bifurcations. The X and Y pixelcoordinates of the intersection of the three legs of each minutia can be directlyformatted. Determination of the minutia direction can be extracted from eachskeleton bifurcation. The three legs of every skeleton bifurcation must beexamined and the endpoint of each leg determined. Figure 3 illustrates the threemethods used for determining the end of a leg that is based on a scanningresolution of 500 ppi. The ending is established according to the event thatoccurs first. The pixel count is based on a scan resolution of 500 ppi. Differentscan resolutions would imply different pixel counts.• A distance of .064” (the 32 nd pixel)• The end of skeleton leg that occurs between a distance of .02” and .064” (the10 th through the 32 nd pixels); shorter legs are not used• A second bifurcation is encountered within a distance of .064” (before the 32 ndpixel)Figure 3 M1-378 / ISO 19794-2 Minutiae angle componentsBrad Wing 6/19/10 5:07 PMComment: This information is moved up fromthe annex.