Hello, I have created a proprietary tool to convert existing RTTEX files (made wth RTPack, both compressed and uncompressed) to PNG using JavaScript.
Hope this tool is any use for someone that is lost and doesn't want to download any "shady" executables.

If anyone wants to recreate this, I simply used pako and built-in FileReader functions for it. It's not that hard, and would be a good time to tinker with on an usual afternoon.
Feedback and suggestions are appreciated.

The tool link