## Description

1) Write a function to compute the 7 similitude moment shape descriptors. Test and

compare results on the rectangle box images ‘boxIm[1-4].bmp’ on the website. How

do they change across the box images? Please make sure your function will work with

non-binary (grayscale) imagery (you will need this for later assignments), i.e., do not

use Matlab’s regionprops function for the mean or area in your calculations. [4 pts]

Nvals = similitudeMoments(boxIm1);

2) Using the datafile (eigdata.txt) provided on the WWW site, perform the following

MATLAB commands [1 pt]:

%% Load the data

clear; close all;

load eigdata.txt;

X = eigdata;

subplot(2,1,1);

plot(X(:,1),X(:,2),’b.’);

axis(‘equal’);

%% mean-subtract data

m = mean(X);

Y = X – ones(size(X,1),1)*m;

subplot(2,1,2);

plot(Y(:,1),Y(:,2),’r.’);

axis(‘equal’);

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3) Compute the eigenvalues (V) and eigenvectors (U) of the data (stored in Y) using the

function eig() in Matlab (recall that you use either the covariance matrix or the

inverse-covariance matrix of the data – see class notes). Plot the mean-subtracted

data Y and the 2-D Gaussian ellipse axes for given the eigenvectors in U (you can use

the plot command in Matlab for this). Use the eigenvalues in V to give the

appropriate 3σ (standard deviation – not variance!) length to each axis (did you

compute the eigenvalues from the covariance or inverse covariance of Y? The

eigenvalues will be related but different! See class notes). [4 pts]

[Note: it would also be nice to draw the 3σ ellipse around Y if you can – Google

‘matlab ellipse.m’ for some code if you are interested.]

4) Rotate Y using the eigenvectors to make the data uncorrelated (i.e., project data Y

onto the eigenvectors – see class slides). Plot the results. [2 pts]

5) Turn in all code, printouts of images, and discussion of results. Make a script to do

the above tasks and call needed functions. Upload your code and images to Carmen

(use the required naming convention for your files). [no points for this last step

anymore]

From now on you MUST submit all code and imagery on Carmen and turn in a paper

report in class to receive points on the homework. Any portion missing will result in a 0 for

the assignment!