How to understand image of Fourier transform? When image is transformed using 2d fourier transform we can visualize the output as:



I think I understand correctly that those lines that come from the center represent high frequencies in horizontal/vertical direction when the size value of frequency related the to length of the line.

What the those lines that seem to connect the ends of those lines comming from the center mean?
How is value of sine/cosine visible on this image?
The lines connecting the ends seem also parallel to existing lines with a similar pattern but faded a lot more.

I think they are the 2D equivalent of harmonics.

Maybe start with a generated straight line segment at a small angle, e.g. $\pi / 6$ rad.
Not end-to-end, and maybe not even centered.