LinesmART is a free app i made with some qc image filters. It produces a really nice line art rendering. Its number two of top free apps for graphics and design right now... i'm right next to autodesk sketch book. which i find pretty wicked awesome.
i have a more pro version of this that i'm still working out some bugs. it lets you touch up the line art with a line pen and has smudge and clone stuff like that. just got to make a plugin to store all the presets and save data down.
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