GNU Image Manipulation Program, commonly known by its acronym GIMP, is a free and open-source raster graphics editor used for image manipulation and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is extensible by means of plugins, and scriptable. It is not designed to be used for drawing, though some artists and creators have used it in this way.

NOTE: Im not the developer, i just provide the app.