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Topic: Image rotation detection probelm
Replies: 32   Last Post: Aug 8, 2013 10:46 PM

 Messages: [ Previous | Next ]
 Phillip Posts: 12 Registered: 8/2/10
Re: Image rotation detection probelm
Posted: Nov 26, 2012 11:28 PM

Hi Darren,

Below is a basic function for finding centre of mass, I can not recall where I stole it from. Try to find the centre of mass in a small region of interest around the peak (instead of using the whole array). Just remember to convert back to whole array co-ordinates to give the final displacement.

Phil

function [a,b] = find_com(x,y,A)

% Finds centre of mass of matrix A in x, y index notation

if nargin == 1
A = x;
[Ar Ac] = size(A);
x = 1:Ac;
y = (1:Ar)';
else
y = y(:);
x = (x(:))';
end

sumA = sum(A(:));
if sumA == 0
a = 0;
b = 0;
else
[row col] = size(A);
% Find centroid across columns:
temp = A.*(ones(row,1)*x);
a = sum(temp(:))/sumA;
% Across rows:
temp = A.*(y*ones(1,col));
b = sum(temp(:))/sumA;
end

"Darren g" wrote in message <k8v2ok\$lam\$1@newscl01ah.mathworks.com>...
> Hi Phillip,
>
> Many thanks. Yes. My code is now working after adopting your suggestion for finding the column and row in which the maximum peak intensity is found. For finding the centre of mass of the image to measure the angle of rotation smaller than one degree I am trying the regionprobs but not yet found a way on how to integrate this within my code. Is this the one you mentioned for finding to centre of mass or any other easy way of doing? Your help for this is much appreciated.
>
> Darren

Date Subject Author
6/19/09 Matt
8/2/10 Phillip
12/21/10 chee ali
12/21/10 Phillip
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11/14/12 Darren g
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