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Gomathy

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14 Feb 2013 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young

Hi Dave, a quick update. The log-sample routine works fine for phase correlation too. Thanks,G

11 Feb 2013 Fourier Mellin Image Registration An implementation of Fourier Mellin Phase Correlation for Image Registration Author: Robinson Laundon

Hi Robin, Good work. It would be great if you have any explanation for why this routine doesn't work for 16-bit images? Thanks.GR

10 Dec 2012 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young

Hi David, the correct LP parameters for the earlier post is
rmin = 5;
rmax = 125;
nw = 500;

I tried various ways to measure theta using Phase Correlation. It doesn't work. Can you please look at the test code ?

10 Dec 2012 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young

Hi David, This is Gomathy again. I am trying to use Phase correlation to measure displacements after converting the image into LP. It fails to detect displacement, whereas the same LP converted image works fine for normxcorr2. I am not sure, where am i making mistakes. Here is the test code. I would greatly appreciate, if you can you can please help.

Iref = imread('cameraman.tif');
deg = 73;
I = imrotate(Iref, deg, 'bicubic', 'crop');

rmin = 5;
rmax = 300;
nw = 1500;
xc = size(Iref, 2)/2;
yc = size(Iref, 1)/2;

lp_Iref = logsample(Iref, rmin, rmax, xc, yc, [], nw);
lp_I = logsample(I, rmin, rmax, xc, yc, [], nw);

THETA_F1 =fftshift(fft2(lp_Iref));
THETA_F2 =fftshift(fft2(lp_I));
a1 = angle(THETA_F1); a2 = angle(THETA_F2);
THETA_CROSS = exp(-1* (a1 - a2)); % Phase Difference
THETA_PHASE = abs(fftshift(ifft2(THETA_CROSS)));
[peak, idx] = max(THETA_PHASE (:));
[ypeak,xpeak] = ind2sub(size(THETA_PHASE ),idx);
theta=xpeak-(size(lp_I,2)+1)/2;

24 Feb 2012 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young

Thanks David.

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