Interactive board using a laser pointer

board.py

#!/usr/bin/python3
import cv2
import numpy
import pyautogui

# usage:
# after launch, a shot from the camera appears.
# mark four corners of the projector by clicking in order: top left, bottom left, bottom right, top right
# the program moves mouse when it sees the laser pointer on-screen
# the program never exits (you have to kill it)

# dimensions of the image while being processed
# (set this lower for faster processing. Do not set higher than camera resolution)
in_shape = 640, 480

# dimensions and of the projector screen and its offset in multi-screen layout
out_shape = 1024, 768
out_offset = 1920, 0

tsf = None

def camera(source):
    cam = cv2.VideoCapture(source)
    while 1:
        status, img = cam.read()
        if not status:
            return
        yield img

def move(pos):
	pos = [out_offset[i] + int(out_shape[i] * pos[i] / in_shape[i]) for i in range(2)]
	pyautogui.moveTo(*pos)

def init(img):
	src_points = []
	def onmouse(event, x, y, flags, param):
		if event == cv2.EVENT_LBUTTONDOWN:
			src_points.append((x, y))
			if len(src_points) == 4:
				cv2.destroyAllWindows()
	
	winname = "init"
	cv2.imshow(winname, img)
	cv2.setMouseCallback(winname, onmouse)
	cv2.waitKey()
	dst_points = numpy.array(((0, 0), (0, in_shape[1]), in_shape, (in_shape[0], 0)))
	src_points = numpy.array(src_points)
	tsf, _ = cv2.findHomography(src_points, dst_points)
	return tsf

for img in camera(0):
	if tsf is None:
		tsf = init(img)
	b, g, r = cv2.split(img)
	img = cv2.warpPerspective(r, tsf, in_shape)
	_, img = cv2.threshold(img, 245, 255, cv2.THRESH_BINARY)
	_, contours, _ = cv2.findContours(img, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)
	positions = list()
	for pts in contours:
		if pts.shape[0] > 4:
			rect = cv2.fitEllipse(pts)
			cv2.ellipse(img, rect, 255)
			pos, (w, h), angle = rect
			if 2 <= w <= 10 and 2 <= h <= 10 and 0.5 <= w / h <= 2:
				positions.append(pos)
	if len(positions) == 1:
		move(positions[0])
	# cv2.imshow("warped", img)
	# if cv2.waitKey(1) == 27:
		# break