光流法draw_flow()函数报错

 光流法draw_flow()函数报错

import cv2
from scipy import *


def draw_flow(im, flow, step=16):
    """ Plot optical flow at sample points
    spaced step pixels apart. """
    h, w = im.shape[:2]
    y, x = mgrid[step / 2:h:step, step / 2:w:step].reshape(2, -1)
    fx,fy = flow[y, x].T
    # create line endpoints
    lines = vstack([x, y, x + fx, y + fy]).T.reshape(-1, 2, 2)
    lines = int32(lines)
    # create image and draw
    vis = cv2.cvtColor(im, cv2.COLOR_GRAY2BGR)
    for (x1, y1), (x2, y2) in lines:
        cv2.line(vis, (x1, y1), (x2, y2), (0, 255, 0), 1)
    cv2.circle(vis, (x1, y1), 1, (0, 255, 0), -1)
    return vis
# setup video capture
cap = cv2.VideoCapture(0)
ret, im = cap.read()
prev_gray = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)
while True:
# get grayscale image
    ret, im = cap.read()
    gray = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)
    # compute flow
    flow = cv2.calcOpticalFlowFarneback(prev_gray, gray, None, 0.5, 3, 15, 3, 5, 1.2, 0)
    prev_gray = gray
    # plot the flow vectors
    cv2.imshow('Optical flow', draw_flow(gray, flow))
    if cv2.waitKey(10) == 27:
        break

 

报错：

解决方案行加上.astype(int)就解决了

y, x = mgrid[step / 2:h:step, step / 2:w:step].reshape(2, -1).astype(int) #以网格的形式选取二维图像上等间隔的点，这里间隔为16，reshape成2行的array