Understanding the Differences between 2D FFT and 2D DFT for Image Transforms

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The discussion centers on the confusion surrounding the differences between 2D FFT and 2D DFT in image transforms, particularly regarding a perceived distortion in one of the transforms. The user notes that the distortion arises from discontinuous lines in the grid-copied image, contrasting with the continuous lines in other transforms. They seek clarification on the relationship between these discontinuities and the resulting distortion. A reference to a resource on rotation and edge effects is provided, suggesting that these factors may contribute to the observed differences. Understanding these concepts is crucial for accurately interpreting image transformations in the context of Fourier analysis.
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Confusion with 2D DFT

Hello everyone,

I'm trying to figure out why the third transform in the picture I attach here is different to the other ones, why it's 'distorted'. I know that it's related with the fact that if you copy the image in a grid the resulting image has discontinuous lines, unlike the other two transforms where the resulting lines are continuous, but I can't see the relation with the distortion.

Thank you for any help!
 

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