Manga artist or digital painter? GIMP is the open source alternative to Photoshop if you are using most Ubuntu distros but if you happen to prefer Kubuntu, you can use Krita, the KDE paint and draw program that is better than GIMP and tops Photoshop and Painter in more ways than one. Open source is FREE and you don;t have to worry about technical support because user communities as well as developers from krita.org all assist Krita users to have the best work tool always.