I wrote a tutorial on how to set up image editing and uploading from the front end to the WordPress media library.
I tried to make it as easy as possible while staying away from writing/offering this as a plugin.
Would this be (too) challenging for the average WordPress developer?
https://pqina.nl/blog/edit-images-before-uploading-them-to-your-wordpress-media-library/
I didn't find this hard to follow Rik although your average user might want a plugin to do it for them!
Thanks for the feedback @LukeyTPP, appreciate it. Will look into offering this as a plugin.