Different representations of frequency space of 2D image FFT

1. What does 2D FFT tell you?
2. What does the FFT of an image represent?
3. What is spatial frequency of an image?

What does 2D FFT tell you?

2D FFT (2-dimensional Fast Fourier Transform) can be used to analyze the frequency spectrum of 2D signal (matrix) data. Conversely, 2D IFFT (2-dimension Inverse Fast Fourier Transform) is able to reconstruct a 2D signal from a 2D frequency spectrum.

What does the FFT of an image represent?

The FFT decomposes an image into sines and cosines of varying amplitudes and phases, which reveals repeating patterns within the image. Low frequencies represent gradual variations in the image; they contain the most information because they determine the overall shape or pattern in the image.

What is spatial frequency of an image?

"Spatial frequency" refers to the number of pairs of bars imaged within a given distance on the retina. One-third of a millimeter is a convenient unit of retinal distance because an image this size is said to subtend one degree of visual angle on the retina.