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.