This filter uses the following Gaussian function to compute the filter weights:
G(i,j) = exp ( -((i-u)**2 + (j-v)**2) / (2 * SIGMSQ) )where: (i,j) is a pixel within the filter window, (u,v) is the centre of the filter window and SIGMSQ is set to 4.
The filter weights W(i,j) are the normalized values of G(i,j) over the entire filter window. Hence the sum of all weights is 1.
The grey level of a filtered pixel is the sum of W(i,j)*V(i,j) over all pixels in the filter window, where V(i,j) is the original value at location (i,j).
NOTE: In order to filter pixels located near the edges of the image, edge pixel values are replicated to give sufficient data.