How to draw a polygon using Opencv + Python?

 import numpy as np

import cv2

# ============================================================================

CANVAS_SIZE = (1080, 1920)

FINAL_LINE_COLOR = (0, 255, 0)

WORKING_LINE_COLOR = (127, 127, 127)

# ============================================================================

class PolygonDrawer(object):

    def __init__(self, window_name):

        self.window_name = window_name # Name for our window

        self.done = False # Flag signalling we're done

        self.current = (0, 0) # Current position, so we can draw the line-in-progress

        self.points = [] # List of points defining our polygon

        self.fpoints = [] # List of points defining our polygon

    def on_mouse(self, event, x, y, buttons, user_param):

        # Mouse callback that gets called for every mouse event (i.e. moving, clicking, etc.)

        if self.done: # Nothing more to do

            return

        if event == cv2.EVENT_MOUSEMOVE:

            # We want to be able to draw the line-in-progress, so update current mouse position

            self.current = (x, y)

        elif event == cv2.EVENT_LBUTTONDOWN:

            # Left click means adding a point at current position to the list of points

            print("Adding point #%d with position(%d,%d)" % (len(self.points), x, y))

            self.points.append((x, y))

            self.fpoints.append([x/CANVAS_SIZE[1], y/CANVAS_SIZE[0]])

        elif event == cv2.EVENT_RBUTTONDOWN:

            # Right click means we're done

            print("Completing polygon with %d points." % len(self.points))

            self.done = True

    def run(self, frame):

        # Let's create our working window and set a mouse callback to handle events

        cv2.namedWindow(self.window_name)

        cv2.imshow(self.window_name, np.zeros(CANVAS_SIZE, np.uint8))

        cv2.waitKey(1)

        cv2.setMouseCallback(self.window_name, self.on_mouse)

        while(not self.done):

            # This is our drawing loop, we just continuously draw new images

            # and show them in the named window

            canvas = frame

            if (len(self.points) > 0):

                # Draw all the current polygon segments

                cv2.polylines(canvas, np.array([self.points]), False, FINAL_LINE_COLOR, 2)

                # And  also show what the current segment would look like

                cv2.line(canvas, self.points[-1], self.current, WORKING_LINE_COLOR)

            # Update the window

            cv2.imshow(self.window_name, canvas)

            # And wait 50ms before next iteration (this will pump window messages meanwhile)

            if cv2.waitKey(50) == 27: # ESC hit

                self.done = True

        # User finised entering the polygon points, so let's make the final drawing

        canvas = np.zeros(CANVAS_SIZE, np.uint8)

        # of a filled polygon

        if (len(self.points) > 0):

            cv2.fillPoly(canvas, np.array([self.points]), FINAL_LINE_COLOR)

        # And show it

        cv2.imshow(self.window_name, canvas)

        # Waiting for the user to press any key

        cv2.waitKey()

        cv2.destroyWindow(self.window_name)

        return canvas

# ============================================================================

if __name__ == "__main__":

    cap = cv2.VideoCapture("test.mp4")

    ret, frame = cap.read()

    if ret == False:

        exit()

    

    pd = PolygonDrawer("Polygon")

    image = pd.run(frame)

    cv2.imwrite("polygon.png", image)

    print("Polygon = %s" % pd.points)

    print("Normalized Polygon = %s" % pd.fpoints)