Effects of Sampling and Compression on Human IRIS Verification

The resilience of identity verification systems to subsampling and compression of human iris images is investigated for three high performance iris matching algorithms. For evaluation, 2156 images from 308 eyes are mapped into a rectangular format with 512 pixels circumferentially and 80 radially. For identity verification, the 48 rows nearest the pupil were taken and the images were subsampled by Fourier domain processing. Negligible degradation in verification is observed if at least 171 circumferential and 16 radial Fourier coefficients are preserved, corresponding to sampling at 342 by 32 pixels. With compression by JPEG 2000, improved performance is observed down to 0.3 bpp, attributed to noise reduction without significant loss of texture. To ensure that no algorithm is degraded, it is recommended that normalized iris images should be exchanged at 512 times 80 pixel resolution, compressed by JPEG 2000 to 0.5 bpp. This achieves a smaller file size than the proposed M1 biometric data interchange format