Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
ScreenTray - A better way to capture, annotate and share screenshots
GIMP - GIMP is a multiplatform photo manipulation tool.
Annotate by Convergely - Easily annotate images you get on Slack - just like Skitch
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
Weava - Workspace to highlight, organize & collaborate on your research articles.