Avif Conversion Pipeline

*Used for Manga UP! *.avif images;

1. Converted from AVIF source images to PNG using ImageMagick;
	- magick convert image.avif image.png
2. Used Waifu2x denoise only @ level 2 with CUnet Model.
3. Merged any split dual-pages and fixed up any pages where needed.
4. Converted to 16 Colors Grayscale PNG (4bit), except for (grayscaled)color pages using ImageMagick (Oak releases only).
	- magick mogrify -format png -quality 10 -dither FloydSteinberg -colorspace Gray -posterize 16 -auto-level *.png
5. Lossless Optimizing images using Pingo
	- pingo -sb -strip *.png / pingo -s9 -strip *.jpg (pingo a70) [old releases]
	- pingo -l -s4 (pingo 1.x)

With step 4 & 5 more than 60% file size reduction is achieved. Reducing colors to 16 is quite justified for these high resolution grayscale images, even if you zoom in quite a bit you still won't or hardly see any differences. Color and grayscaled color images are left untouched and are only optimized with Pingo.

* When the page is of a lower resolution, like x1280, and I've notice these, it will be only denoised and optimized and tagged with {LQ}. Meaning these will stay 8-bit (256 colors) PNG images.

* Oakii releases are not posterized to 16 colors (4-bit) and are only lossless optimized after denoising.

1) ImageMagick 7.1.0-43 Q16-HDRI x64 [later versions cause weird graying during avif to png conversions]
2) Waifu2x-caffe
3) Pingo 1.x (old releases used Pingo a70)