Krita is a free and open source sketching and painting program designed for digital artists. It installs across Windows, MacOS and Linux. Their vision for Development of Krita is —
Krita is a free and open source cross-platform application that offers an end-to-end solution for creating digital art files from scratch. Krita is optimized for frequent, prolonged and focused use. Explicitly supported fields of painting are illustrations, concept art, matte painting, textures, comics and animations. Developed together with users, Krita is an application that supports their actual needs and workflow. Krita supports open standards and interoperates with other applications.