Many companies use this software for editing photos.
I use this for our company work and this works perfectly for image editing process.
MagicaVoxel - A free lightweight GPU-based voxel art editor and interactive path tracing renderer.
GIMP - GIMP is a multiplatform photo manipulation tool.
World Machine - Command powerful tools like erosion and advanced colormaps to create terrain heightmaps, meshes, and textures for your game or 3D scene. Download for Free!
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
Hexagon - Hexagon - Box Version
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.