GIMP

GIMP (GNU Image Manipulation Program) is the premier free and open-source alternative to Adobe Photoshop. It offers a remarkably comprehensive set of raster editing tools for photo retouching, image composition, and digital art. Its strengths include high-quality color management, advanced selection tools, customizable brushes, and support for a wide range of plugins and scripts. The community-driven development model means it is constantly improving, though its interface has historically been cited as less intuitive than commercial counterparts.

For students, hobbyists, or professionals on an absolute zero budget, GIMP provides genuine professional-grade capabilities without cost. It requires more investment to learn its workflow but rewards users with powerful, unrestricted editing. It is a testament to the potential of open-source software in the creative field.