同态滤波器在水下图像对比度增强中的应用

Underwater image contrast enhancement by homomorphic filtering

由于受水下照明条件的限制,水下图像一般都有比较严重的由光照不均匀引起的图像降质.同态滤波可以有效地减少亮度不均匀,并对感兴趣的景物进行有效增强.首先使用基于照明反射模型的同态滤波方法,在简要介绍模型的原理、实现过程和特点的基础上,给出了适用的滤波模型和表达式.引入基于小波变换的同态滤波方法,采用高通滤波对小波变换域系数进行处理,在保持图像总体原貌的基础上对图像局部对比度增强效果显著.

A new spatialfrequency analysis method based on wavelets was applied to homomorphic filtering to enhance the contrast of an image.In order to attenuate the low spatial frequencies and amplify the high spatial frequencies,the wavelet analysis coefficients were processed by a highpass filter.So the local uneven distribution due to light source nonuniformity can be reduced and the object feature can be emphasized.Experiments show that the method performs well in enhancing the local contrast while maintaining its global appearance.