box_filter: movsum, movmean, movmin, movmax imguidedfilter: Guided image filter: 利用numpy.linalg.inv避免了使用for循环逐像素求covariance矩阵逆. REF: He K, Sun J, Tang X. Guided image filtering[J]. IEEE transactions on pattern analysis and machine intelligence, 2013, 35(6): 1397-1409. kernel_basis_filter: kernel basis filter tools.