How do you convert an image to base64?

You could use the Scripting feature in order to use the javascript function that does so.

construct.net/en/make-games/manuals/construct-3/scripting/overview

stackoverflow.com/questions/30631927/converting-to-base64-in-javascript-without-deprecated-escape-call

What C3 object ?

Please provide clearer informations regarding what you are trying to achieve and how your project is configured for that currently.

Sure, I can break down the use case described in the original post:

• We're storing the URI of an image resource somewhere in Construct 3 (variable, object data or otherwise).
• We need convert the image that is accessible via the URI to base64.
• We don't want to use plugins to achieve this (or at the very least not non-vanilla plugins).

You recommended using JavaScript to achieve the conversion from image to base64, but my question is how we would be able to access a URI that is stored somewhere in Construct in JavaScript code, given that the URI is stored somewhere in the project.

EDIT:

If it helps, we can imagine for the sake of discussion that the URI is stored in a parsed JSON object that we would want to be able to access via JavaScript, assuming that JavaScript is the only way to achieve the desired result.