Open Educational Resources (OER): Image Editing Tools

Choose between an online photo editor, desktop editor, and web apps. Use Express for a quick version or Editor for a Photoshop-similar experience.
Mobile versions:   
Android        iTunes        Windows

Gravit Designer is a full featured free vector design app right at your fingertip. It is available for different platforms including Mac, Windows, Linux, Chrome and the Web. Comparable to Adobe Illustrator.

Quick editing that allows you to share your photos across multiple social media platforms.
Mobile versions:   
Android        iTunes        Windows

GIMP is a cross-platform image editor available for GNU/Linux, OS X, Windows and more operating systems. It is free software, you can change its source code and distribute your changes. Whether you are a graphic designer, photographer, illustrator, or scientist, GIMP provides you with sophisticated tools to get your job done.

Free online editor supporting PSD, XCF, Sketch, XD and CDR formats. (Adobe Photoshop, GIMP, Sketch App, Adobe XD, CoreIDRAW).

Krita is a professional FREE and open source painting program. It is made by artists that want to see affordable art tools for everyone.

Apply filters, frames, stickers, text, or crop and resize your photos in just a few minutes.
Mobile versions:   
Android        iTunes        Windows

Inkscape is a professional vector graphics editor for Windows, Mac OS X and Linux. It's free and open source. Comparable to Adobe Illustrator.