Resizing Quality

[frer8833]

What filter is "Best Quality (Adaptive)" using? Is it High-Quality Bicubic or something unique? Paint.Net's best quality looks more sharp (jaggy) than the High-Quality Bicubic (blurred) which ImageGlass uses (which is also Microsoft's best quality because it uses Microsoft's filters). For example when zooming with IG in on a curve or white dots they look a little more blurred and less peak white compared to Paint.Net.

Edited May 17, 2023 by frer8833

[Rick Brewster]

I've improved these for the upcoming 5.0.4. The final/stable release is coming very soon, but you can install a beta right now: https://forums.getpaint.net/topic/122507-paintnet-504-beta-build-8529/

 

"Best Quality (Adaptive)" is being renamed to "Adaptive (Sharp)". It uses different filters depending on the scaling factor, and tends toward the sharp side. The filter is chosen by this code: https://github.com/saucecontrol/PhotoSauce/blob/49a40c08f1571213d9f86dc4f155309a17c9e7e3/src/MagicScaler/Utilities/SettingUtil.cs#L23

 

The new default mode is "Bicubic", which is the Catmull-Rom spline documented here https://imagemagick.org/Usage/filter/ . It is identical to WIC/WPF's "HighQualityCubic" mode (ImageGlass is using GDI+, which is much older, and it may not match WIC/WPF).

 

If you need a guarantee of no sharpening (no ringing artifacts), then avoid Adaptive, Bicubic, and Lanczos. Stick to the other options (including "Bicubic (Smooth)").

[frer8833]

Can you add Sinc-filter or something very similar? It is called the gold standard in some article.

 

Is there a big list of old and new filters as plugin for PN? Is there a big list of all filters, including latest from 2023?

 

What can I do with the code you linked to, can I edit the filter values and apply it somehow, maybe with CodeLab?:

 

[Rick Brewster]

From what I understand, implementing a proper sinc filter is an extremely computationally expensive operation because every output pixel must be computed using every input pixel. So it would take forever and is effectively impractical 😂 Approximations are of course used instead.

 

There is no such thing as a "best quality" or "gold standard" filter. It's all subjective, based on the content you're resizing and your own impression of the result.

 

Some good reading material on resizing filters, I highly recommend bookmarking these and at least skimming through them:

• Resampling Filters from the ImageMagick documentation, https://imagemagick.org/Usage/filter/
  • In particular, search the page for the section called Mitchell-Netravali Filter and look at the discussion and the diagram there.
• "The magic kernel" article, https://johncostella.com/magic/
• "Solving the mystery of Magic Kernel Sharp", https://johncostella.com/magic/mks.pdf

If you're exploring this area then it's worth checking out ImageMagick as it has exhaustive capabilities for resizing.

 

I am considering adding the Magic Kernel (probably the "2021" version), but for Paint.NET I need to strike a balance between power, utility, and simplicity. It would be overwhelming and kind of useless to have a list of 50 different resizing kernels to choose from!

 

I'm also considering making it possible to install resizer plugins, which would mean you could get anything you want. I don't have a concrete timeline for that yet.