Pixen

Pixen is an open-source raster graphics editor created by the Open Sword group. It is designed to create and edit pixel art. It runs on Mac OS X. The latest version is Pixen 3.

Pixen utilizes a basic interface similar to that of Adobe Photoshop. While common tools are included in Pixen, such as the pencil, eraser, and fill tool, Pixen also uses a unique left/right tool system. This system enables the user to assign a different tool to the left and right mouse buttons. This can be used effectively when drawing and erasing. It also features several color palettes, as well as integration with Mac OS X's color options.

Unlike most basic bitmap-based applications like Microsoft Paint, Pixen has a layer system that will let you organize parts of an image, name them, or hide them. Again, some of its tools can be compared to Photoshop. The magic wand tool is one that is particularly notable.

Tux Paint

Tux Paint is an open source bitmap graphics editor (a program for creating and processing raster graphics) geared towards young children. The project was started in 2002 by Bill Kendrick who continues to maintain and improve it, with help from numerous volunteers. It is licensed under the GNU General Public License, and seen by many as a free software alternative to a similar commercial educational software product, Kid pix.

Seashore

Seashore is an image editor for Mac OS X, which was influenced by the GIMP and written using the Cocoa API. It is released under the GNU General Public License. Seashore uses GIMP's native file format, XCF, and has support for a handful of other graphics file formats, including full support for TIFF, PNG, and JPEG, and read-only support for BMP, PDF and GIF. Seashore offers a smaller number of features in comparison with GIMP, including layers and alpha channel support, gradients and transparency effects, anti-aliased brushes, tablet support and plug-in filters.

Seashore is currently at version 0.1.9 and is considered to be in Beta stages. It lacks many of the features that GIMP has, but Seashore's purpose is to become an easy-to-use Free Software graphics editor that runs natively on Mac OS X. Currently there is a working version of GIMP for Mac OS X, Gimp.app. Gimp.app has many features that Seashore does not have, but it requires a version of X11 to run. Seashore is written using the native Mac toolkit, Cocoa.

Paint.NET

Paint.NET is an open source, raster graphics editing program for Windows, developed on the .NET Framework. Originally created as a Washington State University student project, Paint.NET has evolved from a simple replacement for the Microsoft Paint program included with Windows into a powerful editor with support for layers, blending, transparency, and plugins.

Paint.NET is primarily programmed in the C# programming language, with small amounts of C++ used for installation and shell-integration related functionality. Its native image format, .PDN, is a compressed representation of the application's internal object format, which preserves layering and other information. Released under the MIT License, Paint.NET is open source software.

mtPaint

mtPaint is a graphic editing program geared towards creating indexed palette images and pixel art. It is aimed to be simple and easy to use.

mtpaint is designed for use on the GNU/Linux and Microsoft Windows computer operating systems, and uses the GTK+ toolkit (version 1 or 2). It was originally created in 2004 and developed by Mark Tyler, but since 2006 it has been maintained by Dmitry Groshev. Released under the terms of the GNU General Public License, mtPaint is free software.