. 2013 Mar 31;2013:107871. doi: 10.1155/2013/107871
Copyright © 2013 M. Gayhart and H. Arisawa.
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Figure 4.
Convolution mask for the gradient.