# No subject

Sun Apr 3 09:54:08 EDT 2011

```"The itk::GradientMagnitudeRecursiveGaussianImageFilter computes the
magnitude
of the image gradient at each pixel location. The computational process is
equivalent to first
smoothing the image by convolving it with a Gaussian kernel and then
applying a differential
operator. The user selects the value of s.

Internally this is done by applying an IIR 1 filter that *approximates a
convolution with the*
*derivative of the Gaussian kernel*. Traditional convolution will produce a
more accurate result,
but the IIR approach is much faster, especially using large ss [21, 22]."

My question:
Is there a filter in ITK that performs the traditional and more accurate
convolution ? I am doing some
curvature calculation in 3D and need to be as accurate as possible. Also,
how do I deal with
different z spacing using this class or other gradient filters ?

Thank you,
Cagatay

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gnitudeRecursiveGaussianImageFilter computes the magnitude</div><div>of the=
image gradient at each pixel location. The computational process is equiva=
lent to first</div>
<div>smoothing the image by convolving it with a Gaussian kernel and then a=
pplying a differential</div><div>operator. The user selects the value of s.=
</div><div><br></div><div>Internally this is done by applying an IIR 1 filt=
er that <b>approximates a convolution with the</b></div>
<div><b>derivative of the Gaussian kernel</b>. Traditional convolution will=
produce a more accurate result,</div><div>but the IIR approach is much fas=
ter, especially using large ss [21, 22].&quot;</div><div><br></div><div>
My question:</div><div>Is there a filter in ITK that performs the tradition=
al and more accurate convolution ? I am doing some</div><div>curvature calc=
ulation in 3D and need to be as accurate as possible. Also, how do I deal w=
ith=A0</div>
<div>different z spacing using this class or other gradient filters ?</div>=
<div><br></div><div>Thank you,=A0</div><div>Cagatay</div>

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```