JuliaLang/julia — pull request #491 by stefan-k (2012-02-28 22:42:16+00:00)
Title: removed fspecial, separate function for each filter kernel

sobel, prewitt, imaverage, imlaplacian, imdog.
also: ssd, sad
imfilter separates kernels if possible

Because the singular values of separable kernels aren't exactly zero, I assume they are if they are smaller than 10^-7 (there might be a better choice for this limit).
I am not sure about the DoG because I don't get the same results as in Matlab. But comparison is hardly possible because the factor sigma2/sigma1 is not known in Matlab (I chose sqrt(2) as factor).