Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
GIMP - GIMP is a multiplatform photo manipulation tool.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
showFoto - ShowFoto is the standalone image editor of the digiKam project.