基于局部直方图均衡化的指纹方向图算法

针对低质量指纹图像的纹理信息和灰度梯度信息遭到严重破坏的问题,提出一种基于局部直方图均衡化的指纹方向图算法.此算法结合指纹谷点与其相邻脊点特有的灰度差规律,修改了经典直方图均衡化的累积分布函数,用于放大源图像的纹理信息,使图像趋于二值化.基于放大的纹理信息,采用改进的点方向图算法计算指纹的谷点方向,使用直方图块方向图法赋予脊点方向,同时校正谷点的点方向,得到完整的方向图.通过对FVC2006指纹库中的部分低质量图像的增强结果进行比较,此算法对低质量指纹图像的增强性能优于传统算法.

Algorithm of fingerprint direction images based on local histogram equalization

Aimed at the problem of serious destruction of the texture and gradient information on low-quality fingerprint images,a algorithm of fingerprint direction images was proposed based on local histogram equalization.According to the specific rule of grey scale difference between valley points and neighboring ridge points on the fingerprint image,the cumulative distribution function of classical histogram equalization was modified for enlarging the weak texture information on the source image graphs and making it approach to binary-coded one.The valley points' direction was evaluated with ameliorative points directed graph algorithm on the basis of enlarged texture information and,then the ridge points' direction with histogram directed graph algorithm.Meantime,the valley points' direction was corrected and a whole directed graph received.The simulation result of some low-quality images in fingerprint database FVC2006 showed that this algorithm was remarkably superior to the conventional ones for enhancing the low-quality fingerprint.