Invision - Prototyping and collaboration for design teams
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
GIMP - GIMP is a multiplatform photo manipulation tool.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.