That is as expected. If you want the DC component to be in the center of the image, you need to do a circular shift of the pixels.
This is not unusual fft behavior. Raw (non-image) FFT functions operating on an ordinary array tend to put the DC component in [0]. It's only if you want a pretty graph that you shift it to look like the center. > On Aug 27, 2015, at 11:23 AM, Jonathan Gibbs <[email protected]> wrote: > > Has anyone played with OIIO's FFT functions? I've not worked with this much, > but what I'm used to seeing out of the FFT is an image with a white pixel in > the center and some matter of pixels around those. > > (For instance: http://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm > <http://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm>) > > What I get out of OIIO is an image with interesting bits in the 4 corners and > nothing in the middle. Am I right to interpret pixel (0,0) as the lowest > frequency in X and Y and pixel (max,max) as the highest frequency in both X > and Y? > > --jono > -- Larry Gritz [email protected]
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