Krita - bitmap editor
Krita is an application for working with raster images. It allows you to both create images from scratch and work with ready-made images. You can work from photos or scans, or start from scratch. Krita directly supports most graphics tablets.
Krita differs from other graphic design programs in that it uses a plug-in brush mechanism. You can use brush files from Gimp, complex imitations of real brushes, or brushes that blend colors or warp the image. In addition, Krita has full support for graphics tablets, including pen pressure, pen tilt and speed, making it a great choice for artists. It has easy-to-use tools for drawing lines, ellipses and rectangles. With plug-in "drawing assistants" you can draw shapes that look like they were drawn by hand.