Thought y'all might appreciate this
https://github.com/0x09/resdet
FAQ
This utility takes an image or frame of video which may have been upscaled and attempts to exactly identify the original resolution.
How?
Traditional resampling methods tend to manifest as an odd extension of a signal's frequency domain combined with a low-pass filter (where the shape of the filter differs among the various resampling methods). Conveniently the Discrete Cosine Transform causes the zero-crossings of this extension to fall at exactly the offset the source was upscaled from. resdet works by trying to identify these inversions.
https://github.com/0x09/resdet
FAQ
This utility takes an image or frame of video which may have been upscaled and attempts to exactly identify the original resolution.
How?
Traditional resampling methods tend to manifest as an odd extension of a signal's frequency domain combined with a low-pass filter (where the shape of the filter differs among the various resampling methods). Conveniently the Discrete Cosine Transform causes the zero-crossings of this extension to fall at exactly the offset the source was upscaled from. resdet works by trying to identify these inversions.