Checking if a point is inside a polygon

Question

I have a class describing a Point (has 2 coordinates x and y) and a class describing a Polygon which has a list of Points which correspond to corners (self.corners) I need to check if a Point is in a Polygon

Here is the function that is supposed to check if the Point is in the Polygon. I am using the Ray Casting Method

def in_me(self, point):
        result = False
        n = len(self.corners)
        p1x = int(self.corners[0].x)
        p1y = int(self.corners[0].y)
        for i in range(n+1):
            p2x = int(self.corners[i % n].x)
            p2y = int(self.corners[i % n].y)
            if point.y > min(p1y,p2y):
                if point.x <= max(p1x,p2x):
                    if p1y != p2y:
                        xinters = (point.y-p1y)*(p2x-p1x)/(p2y-p1y)+p1x
                        print xinters
                    if p1x == p2x or point.x <= xinters:
                        result = not result
            p1x,p1y = p2x,p2y
         return result

I run a test with following shape and point:

PG1 = (0,0), (0,2), (2,2), (2,0)
point = (1,1)

The script happily returns False even though the point it within the line. I am unable to find the mistake

Answer 1

I would suggest using the Path class from matplotlib

import matplotlib.path as mplPath
import numpy as np

poly = [190, 50, 500, 310]
bbPath = mplPath.Path(np.array([[poly[0], poly[1]],
                     [poly[1], poly[2]],
                     [poly[2], poly[3]],
                     [poly[3], poly[0]]]))

bbPath.contains_point((200, 100))

(There is also a contains_points function if you want to test for multiple points)