HOW TO FIND THE FOURIER TRANSFORM OF DIFFERENT SEGMENTS IN AN IMAGE?

I have a matrix of 200 *200 pixels.The marix is divided into 40*40 pixels segments (A masked image) . I want to find the FOURIER TRANFORM of each segment separately and then map them together as a single matrix (200*200 pixel). The matrix looks as I have attached in figure. The circles have lens property so the mapped image will be as spots in the next surface. Please tell me how to do it.

Answer 1

[Vishnu Vardhan]

You can first make a copy of 40*40 pixels segment from the original image by making use of the row number and column number appropriately.

For example , If you want the first 40 rows and 40 columns

partOfImage = originalImage(1:40,1:40)

And then perform fft as you do for any image.