Re:Samsung “space zoom” moon shots are fake, and here is the...
by colanderman on Saturday March 11, 2023 @02:01PM
(#35111435)
> The resulting complex array is than converted into an output image by taking the magnitude.
No, it's emphatically not. Perhaps you are thinking of displaying a spectrogram.
To produce an image from frequency-domain data, inverse DFT must be applied. Since (as @nyanpasu64 points out), the DFT of a real-valued image or kernel is conjugate-symmetric (and vice-versa), the result is again real-valued without loss of information. The phase information is not lost. If it were, the image would be a jumbled mess.
(Not that DFT+inverse DFT is necessary for Gaussian blur anyway -- you simply convolve with a truncated Gaussian kernel.)
> Another point of view is that there are infinitely many images that will produce the same result after blurring.
No, this is not true. I don't know why you think it is. This is only true of a brick wall filter, which Gaussian filter is not [1].
The SNR of high-spatial-frequency components is reduced for sure, which can lead to irrevocable information loss. But this is nothing to do with phase.
No, it's emphatically not. Perhaps you are thinking of displaying a spectrogram.
To produce an image from frequency-domain data, inverse DFT must be applied. Since (as @nyanpasu64 points out), the DFT of a real-valued image or kernel is conjugate-symmetric (and vice-versa), the result is again real-valued without loss of information. The phase information is not lost. If it were, the image would be a jumbled mess.
(Not that DFT+inverse DFT is necessary for Gaussian blur anyway -- you simply convolve with a truncated Gaussian kernel.)
> Another point of view is that there are infinitely many images that will produce the same result after blurring.
No, this is not true. I don't know why you think it is. This is only true of a brick wall filter, which Gaussian filter is not [1].
The SNR of high-spatial-frequency components is reduced for sure, which can lead to irrevocable information loss. But this is nothing to do with phase.
[1] https://en.wikipedia.org/wiki/Window_function#Gaussian_windo...