See http://en.wikipedia.org/wiki/Kuwahara_filter for reference to the original method.
The Imagemagick syntax is as follows:
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convert inputimage -kuwahara Radius resultimage
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convert inputimage -kuwahara RadiusxSigma resultimage
In the Imagemagick implementation sigma is optional and provides a bit of smoothing control that the original method does not include. In the Imagemagick implementation radius+1 is equivalent to the original method's quadrant width.
Examples:
Input:
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convert peppers_colornoise_gauss2.png -kuwahara 2 peppers_kuw_gauss_2.png
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convert peppers_colornoise_gauss2.png -kuwahara 3 peppers_kuw_gauss_3.png
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convert peppers_colornoise_gauss2.png -kuwahara 4 peppers_kuw_gauss_4.png
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convert peppers_colornoise_gauss2.png -kuwahara 5 peppers_kuw_gauss_5.png
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convert peppers_colornoise_gauss2.png -kuwahara 7 peppers_kuw_gauss_7.png
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convert peppers_colornoise_gauss2.png -kuwahara 9 peppers_kuw_gauss_9.png
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