Nyquist frequency from image

Hi..

Is it possible to calculate nyquist frequency or the sampling frequency from image.

Answer 1

[Walter Roberson]

floor(size(YourImage) ./ 2)

[Gova ReDDy]

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]

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.