How to change coordinates?

How to transfer image texture from Cartesian to polar coordinates? I know how to find theta or other mathematical part but in some image i saw researchers convert circle part to a rectangular part by transferring from cartesian coordinate to polar coordinate.

Answer 1

[Ashutosh]

Do you mean to say you want to address using (r,theta) instead of x,y? (hope u didnt mean log polar) If yes, then code as:

r = sqrt(x^2 + y^2) theta = atan(y/x) (make sure x!=0, handle it directly)

Now, I(x,y) can be addressed as I(r,theta)

[Umme Tania]

Thank you, but i already done this part. Can u please read the question again.I edited the question.