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### Image preprocessing  The only preprocessing step used is convolving the image with a \((2n+1)\times(2n+1)\)  kernel where the center element is \(1/(n+1)\) and the k-th layer surrounding the center is made up of values \(1/(8k\cdot(n+1))\). For example, when n=1 the kernel would be \[  \left( \begin{array}{ccc}  \tfrac{1}{16} & \tfrac{1}{16} & \tfrac{1}{16}\\\\