关键词: 互信息, 核密度估计, 图像配准, 快速卷积

Abstract: To estimate mutual information of images rapidly and accurately is one of very important problem in image registration，which involves estimating joint probability density and marginal probability density of two images.Kernel Density Estimator（KDE），however，is computational expensive.This makes it very slow to compute mutual information.In this paper，a fast estimation algorithm is presented which takes advantage of the property of delta function and fast convolution based on fast Fourier transform.The proposed algorithm can estimate mutual information of images with linear time complexity.Experiments show the fast algorithm is very efficient.

Key words: mutual information, kernel density estimator, image registration, fast convolution