Krita

Krita is a free, open-source program designed for digital artists to create digital art files from scratch. It supports various fields like illustrations, concept art, matte painting, textures, comics, and animations. Krita is optimized for frequent use and supports open standards, interoperability with other applications, and is not intended as a replacement for Photoshop. Its tools are primarily relevant to digital painting, concept art, illustration, and texturing.