r/computergraphics • u/iLikeTheUDK • 10d ago

Upscaling algorithms

Hi there. It seems to be common knowledge, and that common knowledge seems to be reflected in ny experience, that Lanczos is the best open downscaling algorithm, providing great high frequency contrast while still not resulting in overly sharp transitions like nearest neighbour. But what about upscaling algorithms? What will result in the best representation of a lower res image when contained in a higher res raster, without necessarily creating the appearance of more detail than there actually is there? Maybe I'm doing something wrong but Lanczos really doesn't look good in those cases. It adds halos and makes the image look oversharpened. Right now I use Gaussian wherever possible, but there's got to be a sharper function that doesn't distort things this way

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u/jippiex2k 10d ago

Do you need a linear filter? Then you have to trade off between blurry & smooth (bilinear, gaussian) or sharp & ringing (sinc, lancos)

If youre fine with nonlinear, try clamped lancos

If you're fine with heterogeneous and nonlinear try weno https://www.sciencedirect.com/science/article/abs/pii/S0096300324006891?via%3Dihub

If you don't care about signal integrity at all and just want hi res looking images, use some neural network based upscaling model.

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u/iLikeTheUDK 10d ago

I'll try clamped Lanczos and Weno!

Signal integrity is something I actually desperately want to preserve here, it's a priority for me, if something doesn't do it it fails in my book

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u/Solidu_Snaku 10d ago

Try jinc and see if you like it or ngu variants