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updownsample

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updownsample

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21 Mar 2004 (Updated )

up/down sample an input matrix using the fourier domain.

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Description

Up/down sample an image/matrix/vector (can be of complex numbers) using the frequency domain.
The matrix/vector should be continuous of a high degree (has continuous derivatives) in order to obtain a reasonable up/down sampling

Speed-up can be achieved if the user up-samples to a near power of 2. no optimization is done inside this code for efficient fft usage.

Documentation is found inside the *.m file.

type "updownsample" for the example

Acknowledgements

Fft Upsample inspired this file.

MATLAB release MATLAB 6.1 (R12.1)
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Comments and Ratings (7)
29 Sep 2010 Aravind Kumar

The code works great ! Thanks.

31 Mar 2010 Sumedh Joshi  
26 Nov 2009 Jong Rah  
14 Sep 2007 Jeroen Corthout  
12 Jan 2005 David Felguera

Problems with circular convolutions ...

Just try:

in_m = ones(10,10);
in_m = [zeros(10,10);in_m;zeros(10,10)];
in_m = [in_m,zeros(30,10)];
figure(100);
imagesc(in_m);
out_x_sz = 320;
out_y_sz = 320;
out_m = updownsample( in_m,out_x_sz,out_y_sz,0,1);
figure(200);
imagesc(out_m);

I dont know exactly if its a circular convolution but it seems to. (could be some kind of aliasing too, when processing some kind of images)

10 Apr 2004 Ahmed Zakzouk

nice work

09 Apr 2004 Aaron Clarke

Nice function. Works great.

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