	HELSINKI UNIVERSITY OF TECHNOLOGY
	LABORATORY OF COMPUTER AND INFORMATION SCIENCE
	NEURAL NETWORKS RESEARCH CENTRE

Exercise from Chap. 3

10. (Page 283):

A digital image contains periodic grid lines in the horizontal and vertical directions with a spacing of 1 cm. The sampling interval is 1 mm, and the size of the image is 20 cm X 20 cm.

The spectrum of the image is computed using the FFT with an array size of
256 X 256, including zero-padding in the area not covered by the original image.

Sketch a schematic diagram of the spectrum of the image, indicating the nature and exact locations of the frequency components of the grid lines.

Propose a method to remove the grid lines from the image.

http://www.cis.hut.fi/Opinnot/T-61.5090/2005/local/Ex3.shtml
jaakko.sarela@hut.fi
Friday, 20-Jan-2006 14:22:09 EET