[HN Gopher] Google researchers detail new method for upscaling l...
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Google researchers detail new method for upscaling low-resolution
images
Author : zonovar
Score : 31 points
Date : 2021-08-31 20:54 UTC (13 hours ago)
(HTM) web link (www.dpreview.com)
(TXT) w3m dump (www.dpreview.com)
| dang wrote:
| We changed the URL from https://petapixel.com/2021/08/30/googles-
| new-ai-photo-upscal..., which points to this. Both articles point
| to this one, which had a recent and related thread:
|
| _High Fidelity Image Generation Using Diffusion Models_ -
| https://news.ycombinator.com/item?id=27858893 - July 2021 (19
| comments)
| [deleted]
| empressplay wrote:
| There might be hope for Star Trek:Deep Space Nine yet!
| dakial1 wrote:
| Some of the images in the article seemed to be high-res images
| that where downscaled to low-res (and it makes sense to see how
| the upscalling process changes the original), but wouldn't that
| make it easier for the ML to revert the downscaling process
| rather than taking an original low-res photo and upscale it?
| lwneal wrote:
| This is true. Downscaling an image and then training a neural
| network to scale it back up is the way single-image
| superresolution systems typically work. Research papers need to
| evaluate their models, and how can you evaluate a scaled-up
| image unless you have the original ground truth to compare it
| to?
|
| This can introduce a dataset shift bias. For example, if you
| train a network to upscale 1080p movie frames to 4k, the
| results might be disappointing when you try to scale 4k to 8k.
| sorokod wrote:
| If we start with multiple source images that are "small" (by some
| definition of small) perturbations of each other and upscale
| them, what can be said about the results?
| emrah wrote:
| It is pretty impressive/crazy how well CDM and SR3 work together
| to go from 32x32 to 256x256 e.g. the Irish Setter. How could the
| algos possibly know the lighter coloring (due to breed or
| lighting) between the dog's eyes?! It's basically inventing
| pixels
| sorokod wrote:
| How confident can you be that the initial 32x32 was an Irish
| Setter?
| shakna wrote:
| Even basic upscaling algorithms can guess a surprising amount
| of detail.
|
| When I was putting together a simple and fast method, a while
| back, I compared my own to the very, very, basic and ended up
| with this [0].
|
| The far left is the original, the others are just shifting the
| scale percentage. There's a surprising amount of detail kept,
| even though all of the algorithms were pushed way beyond what
| should be considered their limits. (Purposefully - to expose
| bias that was easier to analyse.)
|
| [0] https://raw.githubusercontent.com/shakna-
| israel/upscaler_ana...
| emrah wrote:
| Thank you for sharing. Honestly I don't see any "pixel
| divining" in your examples. The algos take existing pixels
| and build on top of that.
|
| Irish Setter example seems to introduce detail that is not
| part of the original small image, like the lighter/whitish
| area between the dog's eyes.
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