基于方向特性的指纹图像预处理

以图像块的灰度均值与标准偏差的比值为判定标准对指纹图像进行分割，本文提出了改进的点方向图计算方法，针对指纹图像方向性强的特点，构造了间隔22．5°的八方向的滤波模板对指纹图像进行方向性滤波，并采用数学形态学的方法进行图像平滑，以自适应阈值法对图像进行二值化。实验结果证明，用该方法进行图像预处理，能大大减少指纹图像中的伪结构，有利于后续的指纹特征抽取和识别，有较高的使用价值。

On Orientation-based Fingerprint Preprocessing

This article carries on the ratio of the block＇ s average grayscale and standard deviation as the determination standard for the fingerprint image segmentation. In view of directivity of the fingerprint image, constructs the eight-directional weight module which gag is 22.5°and some novel methods for direction map calculating, fingerprint image filtering based on direction template , smoothing based on mathematical morphology method and binarization based on auto-adapted threshold method are proposed. Experiments show that the suggested approach can greatly reduce the noises and pseudo-structures, and hence is helpful for the feature extraction and fingerprint identification. So it has high value in practicing.