Many companies use this software for editing photos.
I use this for our company work and this works perfectly for image editing process.
UI8 - Carefully crafted UI design assets
GIMP - GIMP is a multiplatform photo manipulation tool.
UI Movement - The best UI design inspiration, daily
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
UI Garage - Specific mobile and web design patterns for your inspiration
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.