Krita – Fast, Flexible, and Free Photoshop Alternative Built by Artists

Krita (formerly called KImageShop, Krayon) is a free, open-source and cross-platform digital painting software developed by Krita Foundation (part of the KDE Community) from Sweden. It is fully functional, capable of the entire painting process from drafting, lining, coloring to post-adjustment; can draw concept sketch, illustration, cartoon, animation, scene and 3D mapping; supports digital board, pressure sensing, anti-shake, layers, filters, color management, and other functions.