摘要：

针对数字相机拍摄的指纹图像存在脊线和谷线对比度低、抖动模糊等问题,提出一种基于Retinex理论和短时傅里叶变换(STFT)分析的非接触指纹图像增强算法。依据Retinex理论,利用图像各个像素的相对明暗关系消除光照非均衡性影响,提高脊线和谷线的对比度,实现非接触指纹图像的初次增强。采用STFT分析的方法获取指纹图像的方向图、频率图等纹理信息,并据此构建角度滤波器和半径滤波器,对初次增强结果进行频域滤波处理,进一步增强图像对比度,同时有效抑制噪声的干扰。实验结果表明,该算法对非接触指纹图像的增强效果较好,可以有效提高指纹脊线和谷线对比度,较好地保持指纹脊线的连续性,而且平均处理速度比同态滤波和Garbor滤波相结合的方法也略有提高。

关键词: 非接触指纹图像, Retinex理论, 图像增强, 短时傅里叶变换分析, 同态滤波, Garbor滤波

Abstract:

For the low contrast between ridges and valleys,shake blur and other issues of fingerprint images obtained with digital cameras,a contactless fingerprint image enhancement algorithm based on Retinex theory and Short Time Fourier Transform(STFT) analysis is proposed.According to Retinex theory,the non-uniformity effect of the illumination is eliminated by using the relative brightness and darkness of each pixel in the image,and the contrast between ridges and valleys is increased,which enhances the contactless fingerprint image initially.The method of STFT analysis is used to extract the texture information of the fingerprint image,such as orientation map,frequency map and so on.Then the angle filter and radius filter are built to filter the results of initial enhancement in the frequency domain,which further improves the image contrast while effectively suppressing the interference of noise.Experimental results show that the present algorithm has a better performance on contactless fingerprint image enhancement,which can not only effectively improve the contrast between ridges and valleys of fingerprint,but also maintain the continuity of the ridge better,and its average speed is a little faster than the method combining homomorphic filtering and Gabor filtering.

Key words: contactless fingerprint image, Retinex theory, image enhancement, Short Time Fourier Transform(STFT) analysis, homomorphic filtering, Garbor filtering

中图分类号: 

• TP391