forgot to commit geometry.py, oops

1 files changed, 27 insertions, 0 deletions

diff --git a/geometry.py b/geometry.py
new file mode 100644
index 0000000..d69add8
--- /dev/null
+++ b/geometry.py
@@ -0,0 +1,27 @@
+import math
+def distance_point_line(p, l1, l2):
+    # (x - l1.x) * (l2.y-l1.y)/(l2.x-l1.x)   +  l1.y   =  y
+    # x * (l2.y-l1.y)/(l2.x-l1.x) - l1.x * (l2.y-l1.y)/(l2.x-l1.x) + l1.y - y = 0
+    # x * (l2.y-l1.y) - l1.x * (l2.y-l1.y) + l1.y * (l2.x-l1.x) - y * (l2.x-l1.x) = 0
+    # ax + by + c = 0
+    # with a = (l2.y-l1.y), b = -(l2.x-l1.x), c = l1.y * (l2.x-l1.x) - l1.x * (l2.y-l1.y)
+    a = (l2.y-l1.y)
+    b = -(l2.x-l1.x)
+    c = l1.y * (l2.x-l1.x) - l1.x * (l2.y-l1.y)
+
+    d = math.sqrt(a**2 + b**2)
+    a/=d
+    b/=d
+    c/=d
+
+    assert (abs(a*l1.x + b*l1.y + c) < 0.001)
+    assert (abs(a*l2.x + b*l2.y + c) < 0.001)
+
+    return abs(a*p.x + b*p.y + c)
+
+def is_colinear(points, epsilon=1):
+    for point in points:
+        if distance_point_line(point, points[0], points[-1]) > epsilon:
+            return False
+    return True
+