imageproxy VS willnorris.com

I wrote https://github.com/willnorris/imageproxy for exactly this purpose about 10 years ago. It's just been a personal project, but handful of folks have used it over the years. As mentioned below, imgproxy.net is the other pretty popular option, also written in go. Notably, it's backed by Evil Martians (makers of postcss and a bunch of other things), so is a bit more robust, and has gotten a lot more real-world usage and large scales.

If you can't specify the resolution, then there exists tools like imageproxy which is a server which does resizing for you, and sits as a middleman between your client and the API you are requesting images from. I honestly wouldn't bother with this just because lighthouse says that image sizes are a problem. The amount of effort to host an imageproxy like service outweighs the benefits of simplicity in my opinion. So I would only use imageproxy if I'm expecting a lot of visitors using very slow connections or the images you are loading are large (>1 megabyte).

This gem is just a client for using ImageProxy

I've used Imgix on a lot of projects and can't really complain, it's a bit pricey though. If your needs are simple enough you might be able to host your own transform proxy https://github.com/willnorris/imageproxy

You can try ImageProxy. You will need to host it yourself but the original images can come from third parties.

They use libvips for image processing, so is a lot more performant. For my imageproxy project, I opted to stick to pure Go libraries, so it's a bit slower, and doesn't currently support webp output. But I've found sticking to go libraries makes it easier to build and deploy; for example, I currently use it on my personal website as a plugin compiled directly into my Caddy webserver.