def fix_polygon(polygon):
""" Attempt to fix the given polygon.
We return the fixed polygon, or None if we are unable to fix it.
"""
# Start by splitting the polygon up into an exterior ring, and zero or more
# interior rings.
exterior_ring = polygon[0]
interior_rings = []
for ring in polygon[1:]:
interior_rings.append(ring)
# If the exterior ring is invalid, we can't fix the polygon -> give up.
if not is_ring_valid(exterior_ring):
return None
# Check each interior ring, removing any which aren't valid.
fixed_interiors = []
for ring in interior_rings:
if is_ring_valid(ring):
fixed_interiors.append(ring)
# Reconstruct the polygon out of the remaining linear rings.
rings = []
rings.append(exterior_ring)
rings.extend(fixed_interiors)
fixed_polygon = Polygon(*rings)
# Finally, attempt to buffer the polygon, to fix any remaining problems.
try:
fixed_polygon = fixed_polygon.buffer(0)
except GEOSException:
fixed_polygon = None
return fixed_polygon
