Removing parallel edges from binary image This is a binary image. I want to remove the portion in the red region, and keep the one in the green region. 

The red region has the property of double parallel edges, whereas green does not. If someone could suggest an algorithm it would be helpful.
Just a suggestion:


perform binary skeletonization
detect lines as connected sets of pixels
for every line, find distance to nearest pixel on some other line
compute average distance between inspected line and the nearest line
if the computed distance lays within some predefined interval (say, 3-8 pixels), consider it a double-line and remove both lines


The interval can be determined statistically because double lines have distances forming a distribution, which can be separated well from other line distances in the image.