Create convexify.py

convexify.py

@@ -0,0 +1,32 @@
+def _is_concave(angle):
+    a,b,c = angle
+    ab = (b[0] - a[0], b[1] - a[1])
+    bc = (c[0] - b[0], c[1] - b[1])
+    x = ab[0] * bc[1] - ab[1] * bc[0]
+    return x < 0
+
+def _gen_angles(mutated_border):
+    for i in range(1, len(mutated_border) - 1):
+        a,b,c = mutated_border[i-1:i+2]
+        yield (a,b,c)
+
+def _has_concave_angles(mutated_border):
+    return any(_is_concave(angle) 
+               for angle in _gen_angles(mutated_border))
+
+def _remove_concave_angles(mutated_border):
+    return (mutated_border[:1] +
+            [angle[1]
+             for angle in _gen_angles(mutated_border)
+             if not _is_concave(angle)] +
+            mutated_border[-1:])
+
+#This function assumes that an outer border curls counterclockwise as in KML
+#Additionally, it is designed to only work on boundary segments rather than 
+#on entire boundaries. It made sense at the time and was a good idea in 
+#context. 
+def convexify_segment(mutable_border_segment):
+    mutated_border = mutable_border_segment.copy()
+    while _has_concave_angles(mutated_border):
+        mutated_border = _remove_concave_angles(mutated_border)
+    return mutated_border