Seashore is a free open source graphic editor based on the popular GIMP, native for Mac, that will allow you to work with all your images obtaining fantastic results. This software has been created using Cocoa and offers as many options as possible to its users in what regards to image handling.
Based on the best open source photo editor
The software is capable of using the XCF files from the original GIMP development, as well as other formats like JPEG, PNG or TIFF. It has all the necessary tools, similar to those included in GIMP, like color palettes, modifications and degrading tones, saturation, brushes, anti-aliasing, work by layers, alpha channel,...
Born to improve GIMP.
This program is a perfect alternative for the Mac users that are searching how to handle their images. It has practically all the advances from GIMP, including its great simplicity and easy handling, and since it is open source, it allows the developers to continue developing the software and you to enjoy it without having to spend any money at all.