The page isn't loading for me but I will chime in with an image smoothing optimization trick I've used. If you don't need an exact Gaussian blur you can approx

The page isn't loading for me but I will chime in with an image smoothing optimization trick I've used. If you don't need an exact Gaussian blur you can approximate it very efficiently using integral images: http://en.wikipedia.org/wiki/Summed_area_table http://en.wikipedia.org/wiki/Summed_area_table The more "boxes" you use in your sliding window (analogous to a convolution kernel), the better you can approximate a Gaussian kernel. If you're using a big Gaussian kernel on a big image then integral images can result in a large reduction in the number of operations performed and thus potentially enable a big speed-up.