feat: add WebP + AVIF output encoding (pure-Go, no cgo)

[trungnsbkvn]

Upstream imageproxy decodes WebP but only encodes JPEG/PNG/GIF/TIFF/BMP
(issue #114). This fork adds WebP + AVIF encoders via gen2brain/webp and
gen2brain/avif (libwebp/libaom compiled to WASM, run by wazero) so the
single static binary — built with CGO_ENABLED=0, native Windows — can emit
modern formats for luatsumienbac.vn's self-hosted /media resizer.

[willnorris]

Did you mean to include all the docs that look to be specific to your fork? I'm guess not?

There's some discussion about webp in #388, and I have an experimental webp branch using a different library. I'm not familiar with this one, but will take a look when I get a chance. I think the last one I tried ended up creating files much larger than their JPEG equivalent, so missed all the actual advatnages of webp.

[trungnsbkvn]

My bad,

Not the docs. I was working with my Astro project and found your brilliant work.

[willnorris]

okay, I finally got around to testing the webp and avif implementations, and this is pretty impressive! At least in terms of image quality compared to my previous attempts (#393). It looks to add about 9MB to the total binary size, which isn't great, but it's a 15% increase for supporting modern image formats, so that's not terrible. I still feel a little bit uncomfortable with embedding a wasm runtime in imageproxy, but it's also not the craziest approach for this kind of thing.

I've been spending some time recently on breaking imageproxy into smaller includable modules, so we can make this an optional plugin somehow, so both the increased size and wasm nature are worth a shot here.

One of the first things we'll need to do though is get this PR off of your main branch so that it doesn't include all of these unrelated changes. When I have some time (hopefully tomorrow?) to work on getting this ready to merge, I may just open a new clean PR with just the relevant changes.

so anyway, just wanted to say thanks for the contribution, and I hope to look at it more closely soon. It might have to wait for some of the module work to land, but this is definitely good motivation for me to get that going.

[willnorris]

I just wanted to follow up from my comment yesterday to say that I did get this reworked on top of the modules work. You can see it in the modules branch (this commit specifically).

I even went so far as to update my personal website to that branch and add a global config option to encode all of my images as AVIF, at which point it crashed my little webhost by running out of memory. I haven't dug into it much yet, but it reminded me about one of the reasons I wanted to add module support. While I have a strong preference for no CGO in the core imageproxy build, individual modules could use CGO if needed and users could choose to link them in or not. So that could open up things like using libvips, which is significantly faster.

So, for now you're welcome to try the modules branch if you'd like and see how it performs for you. I definitely need to clean up the modules API quite a bit before I'm ready to merge it into main, and I will probably hold off for a bit on merging this webp/avif implementation. I'd like to look at adding some real benchmarks for image transformation, and do some comparisons of these libraries using purego versus not, as well as some other CGO libraries (now that those are sort of an option).