Convert vector graphics "line drawing" (collection of thin filled polygons) to a true line drawing (collection of paths)

Alec Jacobson

September 10, 2013

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Recently, a colleague found a great collection of clip art "line drawing" svgs. For example, this gorilla: gorilla by melwe I use scare quotes because each line is stylized by a thin black polygon. This way each line can have, for example, varying thickness. In illustrator you can open up this svg, select every thing and give the outline stroke a color to highlight this:

illustrator line drawing to paths

If you zoom in on of the pieces you can see clearly that it's actually a polygon filled with black:

illustrator line drawing to paths

To convert this to a raw collection of paths, first rasterize (dirty I know), by selecting Object > Rasterize... (distinctly not Effect > Rasterize...)

illustrator line drawing to paths

Depending on how detailed your drawing is you may actually have to set the resolution quite low. We want a rough outline after all:

illustrator line drawing to paths

Then click on the rasterized image and select Live trace > Tracing options...

illustrator line drawing to paths

Here is the crucial bit. Uncheck Fill and check Strokes.

illustrator line drawing to paths

This may give you some funny little squiggly lines. I got rid of these by increasing Max Stroke Width, decreasing Min Stroke Length and checking Ignore White.

illustrator line drawing to paths

Finally hit Expand to explode your tracing into the actual curves.

illustrator line drawing to paths

Now that you have paths you can do typical pathy things to them. Like change the stroke width...

illustrator line drawing to paths

Or use a fancy stroke brush ...

illustrator line drawing to paths