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Old 2nd April 2005, 17:12   #19  |  Link
tsp
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Join Date: Aug 2004
Location: Denmark
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remember that a gaussian blur is based on the gaussian function:
1/sqrt(2*pi*SD)*exp(-(x^2+y^2)/(2*SD^2))
radius 1 is then equal to 2 SD(95% of the blurred pixel value is based on the pixels within the radius). An ordinary 1 2 1 kernel is about the same as 0.5 SD^2 1 4 6 4 1 = 1 SD^2 1 8 28 56 70 56 28 8 1 = 2 SD^2 that is for step down on pascals triangle is equal to 1 SD^2 increase.

radius=1 in variable blur is the same as 1/2 SD^2 radius 2 = 1 SD^2 etc. the bigger the radius is the better the binomial blur approaches the true gaussian blur. Also note that variable blur uses a 5x5 kernel for the blur and repeats it to produces higher radius. Due to the greater kernelsize (compaired to a 3x1 kernel in Blur()) rounding error isn't a problem.

Last edited by tsp; 2nd April 2005 at 17:17.
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