While I do not characterized by the drawing, is generally known that every character starts with a sketch on a sheet and then pour it through a scanner to the PC and get the main lines of the drawing.

Separate Line Art is an action that will help the next step, to separate the picture from its background. The process is very tedious and not lose detail.

There is little explanation about it because the picture speaks for itself, and while it is a simple process … what better than to automate it and have ready the graph coloring and give life, no?.
Link : Separate Action Line Art