Is there like a hidden read only property? Or do I genuinely have to find it out for every image outside of script
There isn’t a way, natively: A way to get the width and height of a Texture in pixels
@evaera wrote a NodeJS/express server you can host yourself which figures it out
Theoretically you could maybe implement all that in lua instead of going to an external server, but it would be a project and you’d at least need a proxy server to access roblox.com APIs to download the image data anyways.
Edit: @Jumpathy claims that the original doesn’t work and that they made a version of the plugin that works. I don’t know what the source code is for it, though: