Q2 (a) Explain radial distortion and give two examples of common radial distortion
in digital images.
(4 marks)
(b) Explain the main processing steps in image warping for target-to-source
mapping.
(3 marks)
(c) With the image centre as the origin, the following image matrix of 7×7 pixels
is used as a test image to evaluate the Cartesian to polar transformation
program used in automatic iris recognition.
$$\begin{bmatrix}
0.2 & 0.2 & 0.2 & 0.4 & 0.4 & 0.4 & 0.4 \\
0.2 & 0.2 & 0.4 & 0.6 & 0.6 & 0.6 & 0.4 \\
0.2 & 0.4 & 0.6 & 0.8 & 0.8 & 0.6 & 0.4 \\
0.4 & 0.6 & 0.8 & 1.0 & 0.8 & 0.6 & 0.4 \\
0.2 & 0.4 & 0.6 & 0.8 & 0.8 & 0.6 & 0.4 \\
0.2 & 0.2 & 0.4 & 0.6 & 0.6 & 0.6 & 0.4 \\
0.2 & 0.2 & 0.2 & 0.4 & 0.4 & 0.4 & 0.4
\end{bmatrix}$$
(i)
For the output image represented in the polar co-ordinates, determine
the pixel value at 0 = 160° and r = 2 based on the nearest neighbour
interpolation.
(ii) Repeat (c) (i) for the bilinear interpolation.
(5 marks)
(6 marks)
(d) Based on the results obtained, comment on the likely effects in the output
image caused by the two different interpolation methods.
(2 marks)
TOTAL MARKS FOR Q2: 20