ball_tracking.py

# USAGE
# python ball_tracking.py --video ball_tracking_example.mp4
# python ball_tracking.py

# import the necessary packages
from collections import deque
from imutils.video import VideoStream
import numpy as np
import argparse
import cv2
import imutils
import time

# construct the argument parse and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-v", "--video",
	help="path to the (optional) video file")
ap.add_argument("-b", "--buffer", type = int, default = 64,
	help = "max buffer size")
args=vars(ap.parse_args())

# define the lower and upper boundaries of the "green"
# ball in the HSV color space, then initialize the
# list of tracked points
greenLower=(29, 86, 6)
greenUpper=(64, 255, 255)
pts=deque(maxlen = args["buffer"])

# if a video path was not supplied, grab the reference
# to the webcam
if not args.get("video", False):
	vs=VideoStream(src = 0).start()

# otherwise, grab a reference to the video file
else:
	vs=cv2.VideoCapture(args["video"])

# allow the camera or video file to warm up
time.sleep(2.0)

# keep looping
while True:
	# grab the current frame
	frame=vs.read()

	# handle the frame from VideoCapture or VideoStream
	frame=frame[1] if args.get("video", False) else frame

	# if we are viewing a video and we did not grab a frame,
	# then we have reached the end of the video
	if frame is None:
		break

	# resize the frame, blur it, and convert it to the HSV
	# color space
	frame=imutils.resize(frame, width = 600)
	blurred=cv2.GaussianBlur(frame, (11, 11), 0)
	hsv=cv2.cvtColor(blurred, cv2.COLOR_BGR2HSV)

	# construct a mask for the color "green", then perform
	# a series of dilations and erosions to remove any small
	# blobs left in the mask
	mask=cv2.inRange(hsv, greenLower, greenUpper)
	mask=cv2.erode(mask, None, iterations = 2)
	mask=cv2.dilate(mask, None, iterations = 2)

	# find contours in the mask and initialize the current
	# (x, y) center of the ball
	cnts=cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL,
		cv2.CHAIN_APPROX_SIMPLE)
	cnts=cnts[0] if imutils.is_cv2() else cnts[1]
	center=None

	# only proceed if at least one contour was found
	if len(cnts) > 0:
		# find the largest contour in the mask, then use
		# it to compute the minimum enclosing circle and
		# centroid
		c=max(cnts, key = cv2.contourArea)
		((x, y), radius)=cv2.minEnclosingCircle(c)
		M=cv2.moments(c)
		center=(int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))

		# only proceed if the radius meets a minimum size
		if radius > 10:
			# draw the circle and centroid on the frame,
			# then update the list of tracked points
			cv2.circle(frame, (int(x), int(y)), int(radius),
				(0, 255, 255), 2)
			cv2.circle(frame, center, 5, (0, 0, 255), -1)

	# update the points queue
	pts.appendleft(center)

	# loop over the set of tracked points
	for i in range(1, len(pts)):
		# if either of the tracked points are None, ignore
		# them
		if pts[i - 1] is None or pts[i] is None:
			continue

		# otherwise, compute the thickness of the line and
		# draw the connecting lines
		thickness=int(np.sqrt(args["buffer"] / float(i + 1)) * 2.5)
		cv2.line(frame, pts[i - 1], pts[i], (0, 0, 255), thickness)

	# show the frame to our screen
	cv2.imshow("Frame", frame)
	key=cv2.waitKey(1) & 0xFF

	# if the 'q' key is pressed, stop the loop
	if key == ord("q"):
		break

# if we are not using a video file, stop the camera video stream
if not args.get("video", False):
	vs.stop()

# otherwise, release the camera
else:
	vs.release()

# close all windows
cv2.destroyAllWindows()