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## Homework Statement

I'm working on a Matlab problem for a digital image processing class. The problem is to take an image, then take its 2D-FFT and offset the phase component by pi. Then to take the IFFT of the new DFT using the unmodified magnitude and modified phase.

What I got was a matrix of all zeros! -- A black image.

I'm not sure if this is the correct result, so I'm here. I notice that when I slowly change the phase offset towards +Pi it fades out.

This is a specific problem, but what I really want to know is:

**In general**, how does a phase offset of pi radians to the DFT phase component affect the original image?

## Homework Equations

## The Attempt at a Solution

superman is an image we were given for this assignment

Matlab Code:

superman = imread('superman.png')

supermanDFT = fft2(superman);

supPhase = wrapTo2Pi(angle(supermanDFT) +pi);

supMag = abs(supermanDFT);

newSupermanDFT = supMag.*exp(1i*supPhase);

newSuperman = ifft2(newSupermanDFT);

newSuperman = real(newSuperman);

imshow(uint8(newSuperman))

I checked the code by using no phase offset --basically decomposing the image into phase and magnitude reconstructing the DFT with

*newSupermanDFT = supMag.*exp(1i*supPhase);*and taking the inverse and looking at the image. I got the original image as expected. This doesn't guarantee the code is correct, but I have no reason to think its wrong. I'm not really sure what the result should be. :(

Thanks for any help.