I got tired of tools like these uploading data to a server, so I started building them with a simple constraint: if the task doesn't need a server, don't use one.
That turned into Manic Inventor, a collection of free tools that run locally in the browser.
Image to Data URI is one of the newer ones: https://imagetodatauri.com/
I'd be interested in feedback on whether this local-first approach is actually useful to other developers, and which tools are missing.