In this one, i's are nearly illegible, but are corrected. It appears to be correct here, but could be wrong.
https://blog.adobe.com/hlx_fa6ee5a67d3f2e5b1945745176e6b955e...
This one's weirder. In the original, I can't read many of the letters. It looks like G[EL]NE[XR]A[IL]DI[ER][XK][IT]OR - lots of guesses. The enhanced version is GENERALDIREKTOR (I think). At any rate, it's much more confident in the spelling than I am, as a human.
https://blog.adobe.com/hlx_a337d462293b51f4d91182cbbebf68cf4...
Those images show an effect that looks similar to LCD subpixel rendering, which is an artifact of a scanner working at the limit of what it's sensor is capable of producing (typical CCDs have subpixel stripes (or arrays), just like LCD screens.
Scanners typically overcome this by oversampling and then downsampling the raw data to smooth out the effect. In theory you could also do this with less oversampling if you could manage to get the scanner to do subpixel offsets, and oversampling isn't needed at all if the CCD doesn't use striping or a Bayer array but instead layers the RGB detectors on top of each other, like the Foveon X3 CCD.
Anyway, it is pretty clear that the main benefit of the upsampling interpolation in these particular images is in correcting these subpixel color fringes. Downsampling back to the original resolution should still yield an improved image, which is quite intriguing.
https://www.youtube.com/watch?v=c0O6UXrOZJo
>On the scale of things too horrible to contemplate, "document-altering scanner" is right up there with "flesh-eating bacteria". Since 2006, Xerox scancopiers literally are making stuff up. They, for example, replace digits with others in scans.
Really glad to see they included Lanczos. It's extremely frustrating to those in the know to see comparisons that only use subpar algorithms. The worst only use a B-spline or nearest-neighbor upscale, and end up looking like one of those eyeglass prescription ads for seniors. Something like Lanczos is the minimum acceptable, I think.
Adobe's bicubic produces obvious severe artifacts, I assume it's something like a Catmull-Rom spline cubic.
Aren't those comparisons misleading though? The ML sample is 4x the resolution, comparing to something that is supposed to be used to also make something 4x the resolution. They aren't upsampling the comparison, so I don't know what they're actually doing with it. It's so misleading I just assume the company is scummy.
Even better comparisons are in the blog post for a competing product: https://www.pixelmator.com/blog/2019/12/17/all-about-the-new... (likely the same algorithm, but using a different training set, so results will be different from what Adobes product does).
It has comparisons with nearest neighbor, bilinear and Lanczos filters and uses a slider to make it easier to see the difference.
Papers on this task: https://paperswithcode.com/task/image-super-resolution