@BarryBPS uploaded.png is the original file you upload and will never be amended by Evolve.
The file original.png does get modified if you crop the image use Evolve’s ‘image crop’ functionality.
Note that although uploaded.png exists in the course .zip file when you publish, it will never get downloaded by a learner when they view the course.
It’s exported in the course .zip to allow the course to be imported back into Evolve with all the original assets intact.
So, you could actually delete all copies of uploaded.png from a published Evolve course to reduce the course .zip file size and speed up the process of uploading the course to your LMS - but with the caveat that if you re-import that .zip you will lose the uploaded.png for all assets in the course (even if they already existed on your Evolve instance)
Compressing your images using something like tinypng before uploading them into Evolve is definitely recommended - particularly for PNG files which always seem to get exported from tools like Photoshop with really high file sizes.
Choosing an appropriate image format can also help… typically jpeg is the best format for purely photographic images (that have no transparency). I’d really like to get support for WEBP images added to Evolve soon as they seem to be the best all-round choice - and are now supported by all current browsers (except, for some reason, Safari on macOS v10)