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Scaling sprites by combining waifu2x and xBRZ output

User is offline   MrFlibble 

  • 551

#31

View PostMrFlibble, on 04 October 2018 - 10:11 AM, said:

It's also worth noting that I tried scaling up Doom sprites, with the results broadly similar to what another user achieved with NVIDIA GameWorks Super Resolution neural network scaling (I doubt that one was trained on anime images).

Further on this, I tried scaling up some Doom textures and I have to say there's a noticeable difference, namely, waifu2x blurs colours a lot, especially at low contrast arear whereas the NVIDIA network keeps the image sharp, even though there's some notable ringing sometimes.
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User is offline   MrFlibble 

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#32

Alrighty, following some feedback from the discussion in the NVIDIA GameWorks SuperResolution thread I'm trying to figure out how to counter the blur produced by waifu2x (other than attempting to retrain it using different images, I'm feeling ready to try that out yet).

The thing is that the NVIDIA nework is indeed capable of creating images that appear more or less redrawn at higher resolution by hand (check out a couple of comparisons I posted here), while waifu2x, while creating smooth curves, produces a generally blurry image. Adding noise only partially addresses this issue.

There are filter called Rock in IrfanView which creates a kinda-sorta emboss effect, accentuating edges of areas with different colours. I quickly ran this with a previous monster test:
Spoiler

The image was scaled up 4x with waifu2x and then the Rock filter was applied at 4x. I scaled it back down to 2x with Sinc3. Ignore the greenish halo at some of the sprites' edges, this was a quick test without the extra steps to remove those.

I'm not completely happy with the result though. Is there another way to get rid of the blur towards a pixel art-esque sharpening effect? Simply sharpening the image or applying unsharp mask filters doesn't quite cut it. A simple conversion of the resized image to the 8-bit palette also contributes very little to removing the blur.
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User is offline   Phredreeke 

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#33

The green lines are caused by the surrounding pink background. To get around that I think you would need to upscale only the luma channel and use something else for color. Alternatively you could expand the image onto the background and then apply the original mask later.
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User is offline   MrFlibble 

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#34

View PostPhredreeke, on 16 October 2018 - 11:23 AM, said:

Alternatively you could expand the image onto the background and then apply the original mask later.

Yes, this is about how I do this. I was too lazy to process the image above this way for the test purposes.

Anyway, concerning the Duke3D sprites, using the rock filter as described above doesn't seem to positively contribute to image quality. In fact the result is rather similar to what the original unsmoothed image gets when scaled up.

Another thing to note is that the results of waifu2x scaling with xBRZ smoothing on the sprites' edges do not appear much different from what you get if you plain scale up the same shape in xBRZ:
Spoiler

(waifu2x processing above, xBRZ below)

This is a bit disappointing since I was kinda hoping that the smoothed waifu2x would get better results with various curves and straight lines at odd angles, but it only seems to work with images baked into a background.
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User is offline   Phredreeke 

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#35

still would like to see it in-game :P
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User is offline   MusicallyInspired 

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#36

Worst-case scenario you have to do a bit of pixel editing on the frames. It's a high order to get supreme results from mere filters alone anyway.

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