Mac OS X Softwares to Smooth lines

Gimp Painter is a discontinued fork of GIMP specifically enhanced with tools for digital painting and drawing. It aimed to provide artists with advanced brush capabilities and performance optimizations tailored for creative workflows on the GIMP platform.

FireAlpaca is a free digital painting and drawing software available for both Windows and Mac. Designed with simplicity in mind, it offers core drawing tools and features like layers, brushes, and tablet support, making it accessible for beginners learning digital art.

Clip Studio Paint, formerly Manga Studio/ComicStudio, is a comprehensive digital art software tailored for creating comics, manga, and general illustrations. It offers a powerful suite of tools for sketching, inking, coloring, and panel layout.

Autodesk SketchBook is a powerful yet intuitive digital drawing and painting application designed for artists, designers, and creative professionals. It offers a comprehensive suite of tools to create stunning artwork on various platforms, focusing on a natural drawing experience.