Donald M. Monro

DCT-Based Iris Recognition

This paper presents a novel iris coding method based on differences of discrete cosine transform (DCT) coefficients of overlapped angular patches from normalized iris images. The feature extraction capabilities of the DCT are optimized on the two largest publicly available iris image data sets, 2,156 images of 308 eyes from the CASIA database and 2,955 images of 150 eyes from the Bath database. On this data, we achieve 100 percent correct recognition rate (CRR) and perfect receiver-operating characteristic (ROC) curves with no registered false accepts or rejects. Individual feature bit and patch position parameters are optimized for matching through a product-of-sum approach to Hamming distance calculation. For verification, a variable threshold is applied to the distance metric and the false acceptance rate (FAR) and false rejection rate (FRR) are recorded. A new worst-case metric is proposed for predicting practical system performance in the absence of matching failures, and the worst case theoretical equal error rate (EER) is predicted to be as low as 2.59 times 10-1 available data sets

A model for interpreting fingerprint topology

Abstract A simple mathematical model is developed which computes fingerprint local ridge orientation from core and delta positions. This model provides an intelligent tool for resolving ambiguities due to the periodic nature of orientation, in algorithms for interpreting fingerprint patterns.

Fractal approximation of image blocks

A method for block coding of images based on a least squares fractal approximation by a self-affine system (SAS) is presented. The computational cost of the approximation is linear in the number of pixels in the image. The approximation to a rectangularly tiled block involves evaluating various low-order moments over the block, and solving a system of four linear equations for each tile. The method is applied to a standard test image and the effects of various optimizations are shown. A quantitative comparison with the adaptive discrete cosine transform at 8:1 compression is made. The fidelity of the fractal method shows promise and its greater speed and simplicity compared to other fractal transforms suggest immediate applications such as interactive browsing of remote image archives or image representation in multimedia systems.<<ETX>>

An Evaluation of Image Sampling and Compression for Human Iris Recognition

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 irises from the extended Chinese Academy of Sciences Institute of Automation database were mapped into a rectangular format with 512 pixels circumferentially and 80 radially. For identity verification, the 48 rows that were closest to the pupil were taken and images were resized by subsampling their Fourier coefficients. Negligible degradation in verification is observed if at least 171 circumferential and 16 radial Fourier coefficients are preserved, which would correspond to sampling the polar image at 342 times 32 pixels. With JPEG2000 compression, improved matching performance is observed down to 0.3 b/pixel (bpp), attributed to noise reduction without a significant loss of texture. To ensure that the iris-matching algorithms studied are not degraded by image compression, 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 ANSI/INCITS 379-2004 iris image interchange format.

A hybrid fractal transform

A generalization of fractal coding of images is presented in which image blocks are represented by mappings derived from least squares approximations using fractal functions. Previously known matching techniques used in fractal transforms are subjects of this generalized method, which is called the Bath fractal transform (BFT). By introducing searching for the best image region for application of the BFT, a hybrid of known methods is achieved. Their fidelity is evaluated by a root-mean-square error measure for a number of polynomial instances of the BFT, over a range of searching levels using a standard test image. It is shown that the fidelity of the fractal transform increases with both search level and order of the polynomial approximation. The method readily extends to data of higher or lower dimensions, including time as an image sequences.<<ETX>>

On the space of orthonormal wavelets

The space of orthonormal wavelets is described by a set of parameters for which a simple recurrence generates the coefficients for all orthonormal perfect-reconstruction FIR filters of arbitrary length. The space splits into two halves, each containing the time reverse of the others filters. A MATLAB implementation is given. This paper considers the generation of two-channel perfect reconstruction quadrature mirror filter banks corresponding to compactly supported orthonormal wavelets.

Eyelash Removal Method for Human Iris Recognition

A novel eyelash removal method for preprocessing of human iris images in a human iris recognition system is presented. The method filters each occluded pixel along an axis perpendicular to the eyelash direction, and accepts the filtered value if it changes by more than a certain threshold. This allows partially occluded regions of the iris to be included in iris coding which would previously have been excluded. The method is applied with three iris coding algorithms on an extended 308 class CASIA database and large improvements are shown in the matching performance of two methods, with a modest improvement in the third.

Improved matching pursuits image coding

This paper reports improvements in compression of both inter- and intra-frame images by the matching pursuits (MP) algorithm. For both types of image, applying a 2D wavelet decomposition prior to MP coding is beneficial. The MP algorithm is then applied using various separable ID codebooks. MERGE coding with precision limited quantization (PLQ) is used to yield a highly embedded data stream. For inter-frames (residuals) a codebook of only 8 bases with compact footprint is found to give improved fidelity at lower complexity than previous MP methods. Great improvement is also achieved in MP coding of still images (intra-frames). Compared to JPEG 2000, lower distortion is achieved on the residual images tested, and also on intra-frames at low bit rates.

An effective human iris code with low complexity

A human iris coding technique is reported based upon differences in the power spectrum of fragments from normalized iris images. The procedure has been applied to a set of 2174 images from 308 eyes and tuned over a range of parameters. For identity recognition, 100% correct recognition is achieved using a weighted Hamming distance metric. For identity verification, a variable threshold is applied to the distance metric and the false acceptance and false rejection rates are recorded. After tuning the various parameters, the method achieves the lowest false acceptance rate at the point of first false rejection amongst the three algorithms tested, as well as the lowest complexity.

Rendering algorithms for deterministic fractals

Heavy computation requirements have inhibited the application of fractal technology, but new algorithms for coding and displaying iterated function system fractals are achieving real-time performance in software. We discuss the standard rendering algorithms and introduce a variation that performs a minimal number of arithmetic operations when constructing an approximate fractal. In addition, we describe novel extensions that let us render gray-scale and color fractal images. >