Furthermore I would suggest the following items ^^:

• Better color blending capabilities. Many artists don't like blending colors as the same manner as old version of Photoshop, but prefer the Sai/Opencanvas system. I'm speaking about a brush-mixer for pulling, pushing, mixing the colors and painting at the same time without having recourse to an heavy real simulation. The actual color smudge brush is not very good for this purpose and feels "incomplete".
• Perspective rules (like Mangastudio): http://www.youtube.com/watch?v=BSqxuZkwEv4
• "Wet edges/fringe" (like Photoshop and Sai) to emulate watercolors. http://forum.kde.org/viewtopic.php?f=139&t=89749&p=167716&hilit=watercolor#p167716

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Enrico Guarnieri "Ico-dY"
www.turnangel.com