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