dual tree meaning in English

两层分采采油树

At first we improve the methods of iris image preprocessing , including an efficient arithmetic of evaluation iris images , an improving method of locating iris , calibrating iris image by the translation of coordinate and the circular shift of code , a eatimate of the background illumination by bicubic spline , and the image enhancement by the dual tree complex wavelet transform . next we designed the recognition arithmetic based on the location of the local maxima of the wavelet transform modulus . in the thesis lots of simulation are performed by means of matlab and visual c + +
首先改进了虹膜预处理方法,实现了一种快速高效的虹膜质量评价算法;设计了一种改进的两步虹膜定位算法,准确的定位了虹膜的内外边界;利用坐标转换和编码的循环移位实现了对虹膜图像的配准;利用双三次样条函数拟合虹膜图像背景,去除了非均匀光照对虹膜识别的影响;使用二分树复数小波方法增强了虹膜图像的对比度;在识别算法方面,本文设计了一种“基于小波模极值点位置的虹膜识别算法” 。