LodePaint is an image editor for general purpose image editing, with a focus on pixel art. It supports such features as easy per pixel editing, editing High Dynamic Range photo's, many filters and tools, and plugin support.
The only library dependencies it has are SDL and OpenGL, and LodePaint works on any system supporting those. Its GUI is rendered entirely with OpenGL. Some extra file formats depending on other libraries are provided as a plugin instead, but PNG, BMP, TGA and RGBE import/export, and GIF and JPEG import are available in the core without usage of external libraries.