Visily - The easiest and most powerful wireframe software for agile teams.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
PSD to Sketch Design Converter - Convert a Photoshop design to a layered Sketch file for free
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
Learn SpriteKit by Design+Code - Make a platformer iPhone game from scratch in Swift 4.
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.