<div>Hi David, </div><div><br></div>I struggled with the Gaussian filtering in ITK before.<div>The discrete gaussian filter gives you the option for</div><div> setting the maximum kernel size implicitly by using </div><div>
the maximum error in the approximation. There is </div><div>also SetMaximumKernelWidth that can be used to</div><div>set the upperbound on the kernel size. My understanding </div><div>is that based on these options the kernel size is </div>
<div>automatically set for the discrete gaussian filter. </div><div><br></div><div>Perhaps the API should be updated so that the filters</div><div>match each other. It is disturbing to use setsigma or </div><div>setvariance depending on the smoothing filter you </div>
<div>are using. </div><div><br></div><div>Cheers,</div><div>Cagatay</div><div><br><div class="gmail_quote">On Mon, Jul 23, 2012 at 9:34 AM, David Doria <span dir="ltr"><<a href="mailto:daviddoria@gmail.com" target="_blank">daviddoria@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">In both SmoothingRecursiveGaussianImageFilter and DiscreteGaussianImageFilter, there is a single parameter, 'sigma' (in SmoothingRecursiveGaussianImageFilter) and 'variance' (in DiscreteGaussianImageFilter). In both cases, this is the variance of the Gaussian kernel that is to be used. However, I don't see a way to set the discrete size of the kernel to be used? That is, if you apply a sigma=10 kernel with a 10x10 kernel, that will produce a very different result than applying a sigma=10 kernel with a 2x2 kernel. Is this kernel size automatically set based on sigma/variance?<div>
<br></div><div>A related question - with variance=0, the output of DiscreteGaussianImageFilter is an unmodified version of the input image. However, with sigma=0, the output of SmoothingRecursiveGaussianImageFilter is simply an all black image. Is this a bug? Or does it mean that there is a different interpretation of sigma vs variance in these filters?<br clear="all">
<br>Thanks,</div><div><br>David<br>
</div>
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