Wikipedia
Pixelmator
Pixelmator is a graphic editor developed for Mac OS X by Lithuanian brothers Saulius and Aidas Dailide, and built upon a combination of open source and Mac OS X technologies. Pixelmator features selection, painting, retouching, navigation, and color correction tools; as well as layers-based image editing, GPU-powered image processing, color management, automation, and a transparent head-up display user interface for work with images. Pixelmator uses Core Image and OpenGL technologies that use the Mac's video card for image processing.
Pixelmator was the first commercial image editor to fully support the WebP image format on Mac.