Discord open-sourced a supposedly high-performance image resizer https://github.com/discordapp/lilliput https://blog.discordapp.com/how-discord-resizes-150-million-images-every-day-with-go-and-c-c9e98731c65d
@sivy @Gargron yep there's a CLI: https://github.com/imazen/imageflow#using-imageflow_tool
In addition there's a JSON API server, and native embeds e.g. for Ruby