Many companies use this software for editing photos.
I use this for our company work and this works perfectly for image editing process.
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.
UI8 - Carefully crafted UI design assets
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.
UI Garage - Specific mobile and web design patterns for your inspiration