Darktable - darktable is an open source photography workflow application and raw developer.
Pixelitor - Pixelitor is a cross-platform raster graphics editor written in Java.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
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.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
RealWorld Photos - RealWorld Photos is an free portable photo editor for Windows.