OpenCV + OpticalFlow (DIS Optical Flow、高速、精度低め、バランス良し)

import numpy as np
import cv2 as cv
import time

def draw_flow(img, flow, step=16, elapsed_time=0):
    h, w = img.shape[:2]
    y, x = np.mgrid[step/2:h:step, step/2:w:step].reshape(2,-1).astype(int)
    fx, fy = flow[y,x].T
    lines = np.vstack([x, y, x+fx, y+fy]).T.reshape(-1, 2, 2)
    lines = np.int32(lines + 0.5)
    vis = cv.cvtColor(img, cv.COLOR_GRAY2BGR)
    cv.polylines(vis, lines, 0, (0, 255, 0))
    for (x1, y1), (x2, y2) in lines:
        cv.circle(vis, (x1, y1), 1, (0, 255, 0), -1)
    cv.putText(
        vis,
        f'elapsed_time: {elapsed_time:.2f} ms',
        (10, 30),
        cv.FONT_HERSHEY_PLAIN, 1.5,
        (0, 0, 255),
        1,
        cv.LINE_AA
    )
    return vis

def draw_hsv(flow, elapsed_time=0):
    h, w = flow.shape[:2]
    fx, fy = flow[:,:,0], flow[:,:,1]
    ang = np.arctan2(fy, fx) + np.pi
    v = np.sqrt(fx*fx+fy*fy)
    hsv = np.zeros((h, w, 3), np.uint8)
    hsv[...,0] = ang*(180/np.pi/2)
    hsv[...,1] = 255
    hsv[...,2] = np.minimum(v*4, 255)
    bgr = cv.cvtColor(hsv, cv.COLOR_HSV2BGR)
    cv.putText(
        bgr,
        f'elapsed_time: {elapsed_time:.2f} ms',
        (10, 30),
        cv.FONT_HERSHEY_PLAIN, 1.5,
        (0, 0, 255),
        1,
        cv.LINE_AA
    )
    return bgr

def warp_flow(img, flow):
    h, w = flow.shape[:2]
    flow = -flow
    flow[:,:,0] += np.arange(w)
    flow[:,:,1] += np.arange(h)[:,np.newaxis]
    res = cv.remap(img, flow, None, cv.INTER_LINEAR)
    return res

import sys
cam = cv.VideoCapture(0)
ret, prev = cam.read()
prevgray = cv.cvtColor(prev, cv.COLOR_BGR2GRAY)
show_hsv = False
show_glitch = False
use_spatial_propagation = False
use_temporal_propagation = True
cur_glitch = prev.copy()
inst = cv.DISOpticalFlow.create(cv.DISOPTICAL_FLOW_PRESET_MEDIUM)
inst.setUseSpatialPropagation(use_spatial_propagation)
flow = None
while True:
    ret, img = cam.read()
    gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
    start = time.time()
    if flow is not None and use_temporal_propagation:
        flow = inst.calc(prevgray, gray, warp_flow(flow,flow))
    else:
        flow = inst.calc(prevgray, gray, None)
    elapsed_time = (time.time()-start)*1000

    prevgray = gray
    cv.imshow('flow', draw_flow(gray, flow, elapsed_time=elapsed_time))
    if show_hsv:
        cv.imshow('flow HSV', draw_hsv(flow, elapsed_time=elapsed_time))
    if show_glitch:
        cur_glitch = warp_flow(cur_glitch, flow)
        cv.imshow('glitch', cur_glitch)
    ch = 0xFF & cv.waitKey(5)
    if ch == 27:
        break
    if ch == ord('1'):
        show_hsv = not show_hsv
        print('HSV flow visualization is', ['off', 'on'][show_hsv])
    if ch == ord('2'):
        show_glitch = not show_glitch
        if show_glitch:
            cur_glitch = img.copy()
        print('glitch is', ['off', 'on'][show_glitch])
    if ch == ord('3'):
        use_spatial_propagation = not use_spatial_propagation
        inst.setUseSpatialPropagation(use_spatial_propagation)
        print('spatial propagation is', ['off', 'on'][use_spatial_propagation])
    if ch == ord('4'):
        use_temporal_propagation = not use_temporal_propagation
        print('temporal propagation is', ['off', 'on'][use_temporal_propagation])

cv.destroyAllWindows()