How to use automated flatting tools

Even though I decided not to color the Hootie Comics, I spent some time playing with flatting tools. In case you’ve never heard of it, flatting is the preparatory step for coloring line art, where each separate object is filled with a dummy color to make the region easy to select. At that point, the colorist can use the region selections like an airbrush artist uses stencils. Paint away, or use texture maps or whatever, and the stencil keeps you inside the lines.

Flatting by hand is beyond tedious, so I tried a Gimp plug-in that does it automatically. (There are similar plug-ins for Photoshop). My first impression of it was that it’s too primitive to be useable. But after fiddling with it, I figured out how to coerce it into working.

The scripts basically work by flood-filling every white area with a random color, then they grow the regions so the color changes are hidden underneath the black lines. With this in mind, you have to make a copy of the line art layer and prepare it for the flatting robot, then turn the robot loose on the simplified copy of the line art, not the line art itself. You prepare the dummy line art by closing every not-quite-closed polygon, so the
flood-fill doesn’t find its way out thru the gap. You also have to erase any hatching or cross-hatching, to prevent the robot trying to fill in each tiny white cell with a different color. Then you run the flatting script on your doctored-up layer. The script is slow (hours for a page), so go do something else, or run it before you go to sleep. When the robot is finished, you can delete the doctored-up line art layer.

You will have to clean up after it. Sometimes you will have forgotten to close a polygon. Sometimes you have to use the flood fill to make a bunch of polygons the same color, because the robot has no way of knowing that these polygons all belong to the same object. It’s clunky but it’s workable.

Flatting is not only good for color, it’s also useful if you want to digitally add gray wash or zip-a-tone to your line art. If you set the pressure on your stylus to control opacity and use the selections to keep you in the lines, the digital gray wash looks pretty close to what you could do with diluted ink.

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