基于方向图的指纹预处理方法研究

预处理是指纹自动识别系统中非常关键的部分,它直接影响着指纹识别的最终效果。指纹预处理一般包括规格化、方向图计算、图像分割、滤波、二值化等环节,该文系统地讨论了各环节的有效算法。针对以往求取方向图的不足,给出了一种基于灰度统计特性的改进算法;给出了基于方向图的图像分割、方向滤波器模板的设计以及一维局部最大熵选取阈值的二值化方法。通过对上百幅不同质量的指纹图像进行测试,获得了很好的效果。该文方法具有较好的实用参考价值。

On the Orientation-based Fingerprint Preprocessing

Preprocessing plays a key role in the fingerprint identification system,which directly influences the final ac-curacy of fingerprint identification.The preprocessing in an automatic fingerprint identification system usually includes five steps:normalization,directional graph computation,image segmentation,filtering and binarization.In this paper,the ef-fective and efficient algorithms at each step in the orientation-based fingerprint preprocessing are discussed in details.An improved method based on the statistics of the grey scale is proposed to estimate the orientation field of fingerprint image.The image segment based on the directional graph,design of orientation filters and binarization method upon local one-dimensional maximal entropy are also presented.The proposed algorithms have been widely tested and checked for hundreds of fingerprint images and excellent results are obtained.