说明：  利用MATLAB把虹膜图象展开，由一个圆环转变成一个矩形，便于后续操作.简单，经过实验操作证明完全可以实现虹膜图象的展开，实用
(Iris images using MATLAB to start from a circle into a rectangle, to facilitate follow-up operation. Simple experiment to prove after the realization of the iris image can be unfolded, practical)