b$.$ Two $5-$by$-5$ pixel frames from a greyscale video are shown below:

$I_1=\left[\begin{array}{ccccc}9& 3& 6& 2& 3\\ 9& 8& 7& 7& 6\\ 5& 0& 6& 1& 7\\ 0& 0& 4& 6& 0\\ 2& 1& 5& 1& 9\end{array}\right],I_2=\left[\begin{array}{ccccc}2& 9& 0& 2& 2\\ 6& 7& 7& 6& 3\\ 0& 6& 0& 0& 4\\ 0& 2& 6& 2& 5\\ 3& 0& 5& 1& 0\end{array}\right]$

Calculate the similarity of the pixel at coordinate $(3,3)$ in $I_1$ to loca$-$

tions in $I_2,$ and hence, find the corresponding point in $I_2$ to the pixel

at coordinates $(3,3)$ in $I_1.$ Assume that $($i$)$ a $3-$by$-3$ pixel window

is used, $($ii$)$ similarity is measured using the Sum of Absolute Differ$-$

ences $($SAD$),$ and $($iii$)$ that it is only necessary to consider putative

corresponding points in the central $3-$by$-3$ pixels region of $I_2.$

$[4$ marks$]$

Answer

SAD values are:

$\left[\begin{array}{ccccc}nc& nc& nc& nc& nc\\ nc& 36& 42& 33& nc\\ nc& 5& 23& 24& nc\\ nc& 33& 25& 46& nc\\ nc& nc& nc& nc& nc\end{array}\right]$

Hence, corresponding point is at $(2,3).$

Marking scheme