# HW1_solutions - ECE 380 Biomedical Imaging Spring 2010...

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1 ECE 380 Biomedical Imaging Spring 2010 Homework 1 Solutions ________________________________________________________ 1. Introduction to Matlab (20 pts) >> x = phantom(256); >> figure, imagesc(x); 50 100 150 200 250 50 100 150 200 250 i. What are the dimensions of the image? >> size(x) 256 x 256 ii. What is the maximum and minimum pixel value in the image? Minimum value: >> min_value=min(x(:)) >>min_value=-5.5511e-017 Maximum value: >> max_value=max(x(:)) >>max_value=1 iii. Change the colormap to gray and copy the figure to your homework. >> colormap(gray)

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2 50 100 150 200 250 50 100 150 200 250 b) Two-Dimensional Fourier Transforms (15 points) 50 100 150 200 250 50 100 150 200 250 The function fftshift rearranges the outputs of fft2 by moving the zero-frequency component to the center of the array ( bright spot in the middle).
3 50 100 150 200 250 50 100 150 200 250 Most natural images are dominated by the low frequency components which are an order of magnitude greater than the high frequency components making them difficult to visualize. The log10 function reduces the dynamic range of the image hence more details can be seen.

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