Darktable - darktable is an open source photography workflow application and raw developer.
GIMP - GIMP is a multiplatform photo manipulation tool.
Adobe Lightroom - Adobe Lightroom is a family of image organization and image manipulation software.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
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.