[vtkusers] Spatial average image filter?

[TJ Wilkinson]

I have a need for a filter that takes the average of the pixel values
surrounding a single pixel in a rectangular volume and replaces the
original pixel with the average value.  The filter vtkImageMedianFilter3D
seems to be exactly that, except I need the mean, not the median.  Is
there a filter that does this, or do I need to derive my own filter to do
this job?

Thank you for all your help, especially John Biddiscombe and David Gobbi.

Sincerely,
Todd