python - 打开CV错误: error while displaying rectangle

Question

我无法纠正错误。我正在关注官方 opencv python 教程。我在这里传递一个视频并进行 meanshift。

来源:https://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_video/py_meanshift/py_meanshift.html#meanshift

下面是我的代码:

import numpy as np
import cv2

cap = cv2.VideoCapture("slow.mp4")

# take first frame of the video
ret,frame = cap.read()

# setup initial location of window
r,h,c,w = 250,90,400,125  # simply hardcoded the values
track_window = (c,r,w,h)

# set up the ROI for tracking
roi = frame[r:r+h, c:c+w]
hsv_roi =  cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
mask = cv2.inRange(hsv_roi, np.array((0., 60.,32.)),   np.array((180.,255.,255.)))
roi_hist = cv2.calcHist([hsv_roi],[0],mask,[180],[0,180])
cv2.normalize(roi_hist,roi_hist,0,255,cv2.NORM_MINMAX)

# Setup the termination criteria, either 10 iteration or move by atleast 1 pt
term_crit = ( cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 1 )

while(1):
    ret ,frame = cap.read()

    if ret == True:
        hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
        dst = cv2.calcBackProject([hsv],[0],roi_hist,[0,180],1)

        # apply meanshift to get the new location
        ret, track_window = cv2.meanShift(dst, track_window, term_crit)

        # Draw it on image
        x,y,w,h = track_window
        img2 = cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
        cv2.imshow('img2',img2)

        k = cv2.waitKey(60) & 0xff
        if k == 27:
            break
        else:
            cv2.imwrite(chr(k)+".jpg",img2)

     else:
         break

cv2.destroyAllWindows()
cap.release()







 cv2.imshow('img2',img2)

此行显示错误。执行在这一行停止。我也调试过。

错误如下:

OpenCV Error: Assertion failed (size.width>0 && size.height>0) in imshow, file /build/buildd/opencv-2.4.8+dfsg1/modules/highgui/src/window.cpp, line 269
Traceback (most recent call last):
  File "programs/test14.py", line 36, in <module>
   cv2.imshow('img2',img2)
cv2.error: /build/buildd/opencv-2.4.8+dfsg1/modules/highgui/src/window.cpp:269: error: (-215) size.width>0 && size.height>0 in function imshow

Answer 1

在 OpenCV2.4.x 中 rectangle函数返回 None - 就地修改图像。您可以使用 OpenCV3 或稍微修改您的代码:

cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
cv2.imshow('img2',frame)

代替

img2 = cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
cv2.imshow('img2',img2)