Free raster image editors include GIMP and Paint.NET. GIMP is the best free Photoshop alternative, according to DigitalTrends.com. Krita and InkScape are good options for artists. Most operating systems include a default image editor too, such as Paint for Microsoft Windows.
Paint.NET is easier to use than GIMP but has a smaller feature set, according to MaximumPC.com. GIMP has a steep learning curve, making basic editors, such as Microsoft Paint, typically better for simple tasks. GIMP is available for Windows, Mac and Linux, while Paint.NET only works on Windows 7 and later.
Krita is suitable for image editing but puts more emphasis on tooling for digital painting. InkScape works on vector graphics, making it suitable for logos, clip art illustrations and typography.