Re: How to plot image frequency vs row/coloumn?

Greg, very good question. Gamma is a compression that you can use to compress images so that the dark parts are more visible. It's an exponent in an equation like
intensityOut = intensityIn ^ gamma
Here's the defacto FAQ:
http://www.poynton.com/GammaFAQ.html
Look up the advanced properties of your display monitor and you'll see it has a gamma. Cameras also have a gamma usually (meaning a non-unity gamma). Often the gamma of the camera will cancel out the gamma of the display to give an image that looks more linear (twice the signal gives twice the radiance of the scene). For example, camera gamma of 0.45 and display gamma of 2.2 which cancel out to give 1. For image analysis you'd want a linear gamma if you could. Often you don't have that and it's a tutorial in itself (beyond the scope of this comment) on how to handle things if you don't have a linear gamma (which is, unfortunately, much of the time). Sometimes it can be ignored for simple spatial calculations but for intensity calculations or the utmost precision in spatial calculations you can't ignore it.

You are correct that subtracting the mean of the image will reduce the DC spike and allow for better visualization of the spectrum. Good tip.

Andy, here's some untested pseudo code:
meanSubImage = imageArray - mean(mean(imageArray));
fftImage = FFT2D(meanSubImage)
meanColProfile = sum(fftImage, 1); % Sum along rows
meanRowProfile = sum(fftImage, 2); % Sum along columns
figuresc(0.8, 0.8);
subplot(1,2,1);
plot(meanRowProfile);
title('Average profile vertically);
subplot(1,2,2);
plot(meanColProfile);
title('Average profile horizontally');

-ImageAnalyst
.

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