Nyquist frequency from image

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Gova ReDDy
Gova ReDDy 2012-4-13
Hi..
Is it possible to calculate nyquist frequency or the sampling frequency from image.

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Walter Roberson
Walter Roberson 2012-4-13
floor(size(YourImage) ./ 2)
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Gova ReDDy
Gova ReDDy 2012-4-13
like this:
Imgread=imread('My image');
nyquist freq=floor(size(Imgread) ./ 2);
Thanks and can you please provide some explanation or a link regarding this command.
Walter Roberson
Walter Roberson 2012-4-13
Nyquist frequency for N samples is N/2. size() returns the number of samples in each direction, so divide the size by 2 to get the frequency. This corresponds to the maximum frequency reliably expressible, which is the case where alternating pixels are off and on.
Perhaps you don't need the floor(): it depends on how you want to handle the possibility of odd number of pixels in a direction.
Note that the nyquist frequency can be different between horizontal and vertical, which is why multiple values must be returned.

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