OpenCV Optical Flow + py5

optical_flow.py

# https://docs.opencv.org/4.x/d4/dee/tutorial_optical_flow.html

import py5
import numpy as np
import cv2 # opencv-python

cap = None
py5_img = None
prvs_frame = None
reduced_size = 600, 400

def setup():
    py5.size(600, 400)
    py5.launch_thread(open_capture)

def open_capture():
    global cap, hsv
    cap = cv2.VideoCapture(0)
    print('Capture started')

def draw():
    global py5_img, prvs_frame, flow
    py5.background(255, 255, 0)
    ret = False
    if cap:
        ret, frame = cap.read()  # frame is a numpy array
    if ret:
        frame = cv2.resize(frame, reduced_size)
        next_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        if prvs_frame is not None:
            flow = cv2.calcOpticalFlowFarneback(prvs_frame, next_frame, None, 0.5, 3, 15, 3, 5, 1.2, 0)
            vmag, vang = cv2.cartToPolar(flow[..., 0], flow[..., 1])
            hsv = np.zeros_like(frame)
            hsv[..., 1] = 255
            hsv[..., 0] = vang * 180 / np.pi / 2 # 0 a 360 / 0 1 / 0 255
            hsv[..., 2] = cv2.normalize(vmag, None, 0, 255, cv2.NORM_MINMAX)
            bgr = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)
            py5_img = py5.create_image_from_numpy(bgr, bands='BGR', dst=py5_img)
            py5.image(py5_img, 0, 0)
            draw_direction(flow, 100)
            if vmag.mean() > 1:
                print('moved!')
            else:
                print('')
        prvs_frame = next_frame
 
def exiting():   # py5 will call this for clean up on exit
    cap.release()   

def draw_direction(f, s):
    py5.stroke_weight(5)
    py5.stroke(255)
    hw, hh = py5.width / 2, py5.height / 2 
    py5.line(hw, hh,
             hw + f[... , 0].mean() * s,
             hh + f[... , 1].mean() * s)


py5.run_sketch(block=False)