需要整理

Gaussian filter https://en.wikipedia.org/wiki/Gaussian_filter
Laplacian/Laplacian of Gaussian http://homepages.inf.ed.ac.uk/rbf/HIPR2/log.htm
Difference between Mean and Gaussian Filter in Result http://stackoverflow.com/questions/31131672/difference-between-mean-and-gaussian-filter-in-result

mean or median filter for gaussian noise http://stackoverflow.com/questions/20638912/should-i-choose-mean-or-median-filter-for-gaussian-noise

几种filter的比较