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

ANSI/NIST-ITL 1-2011Data Format for the Interchange of Biometric and Forensic Informationincluded for all sampling points in the image, even if the sampling points are atthe edge of the image.For each sampling point in the Region of Interest, distances between ridgepeaks, measured perpendicular to ridge flow, shall be reported in 2-characterdecimal format using units of 10 micrometers (0.01mm). The size of the areaaround the sampling point (window size) used to determine measurements is leftto the discretion of the implementer, and may vary within an image. Unknownvalues shall be set to “XX”. Valid values are therefore “01” (0.01mm) through “99”(0.99mm or greater). (In practice, the actual stored values are likely to be “30” to“70” in most cases (0.3 – 0.7mm).The 2-character decimal wavelength values for each sampling point areconcatenated left to right for all sampling points in a row, with one data entry foreach row. The number of characters in one data entry is twice the number ofsampling points in one row.13.7.19 EFS Field 9.313 Ridge Wavelength Map Format / RWFThis field permits setting the sampling frequency or data representation formatused in Field 9.312 to values other than the defaults. This field is conditional onthe presence of Field 9.312. This field consists of two information items:• The first information item (Sampling frequency / FWS) is set by default to0.41mm (0.016"). This information item may be used to define higherresolution sampling frequencies than the default: valid settings range from“1” (0.01mm) through “41” (0.41mm).• The second information item (Data format / FDF) is optional. It defines theformat used in Field 9.312. The default (and currently the only setting) isthe uncompressed (“UNC”) format 23 .13.7.20 EFS Field 9.314 Tonal Reversal / TRVRidges in friction ridge images are generally represented as dark areas, withvalleys as light areas. This field indicates whether the entire image is reversedtonally (black-for-white). If all or part of the image is reversed tonally, this 1-character optional field is set to the appropriate value from Table 23. Otherwisethis field is omitted.Partial tonal inversion can occur in different ways. If definable portions of theimage are negative, Field 9.357 can be used to define the specific tonallyreversed areas. Note that in some cases, the tonal reversal is so mixed that only•23 This information item is a placeholder. Because of the possibly very large size of RWM, this provides forfuture, more compressed formats81DRAFT 2