Seashore is a free, open-source image editor for built entirely in Cocoa. It features advanced tools like multiple layers and alpha channel editing, alongside basic tools like gradients, textures, text (with subpixel rendering) and brushes.
Seashore keeps getting better! So smooooth - even on old macs! (Fully functional, in-app purchases allow people to support the project - still 100% free).
This is an easy to use but powerful image editor. It supports "layers". Imagine GIMP/Photoshop "light" - most of the features non-professionals need to create awesome images.
This incredible software is originally the amazing work of Mark Pazolli and many others (see the credits in the user guide).