OpenCV Error: (-215)size.width>0 && size.height>0 in function imshow

Question

I am trying to make a face tracker that combines Haar Cascade Classification with Lucas Kanade good feature detection. However, I keep getting an error that I cannot figure out what it means nor how to solve it.

Can anyone help me here?

Error:

line 110, in <module>
cv2.imshow('frame',img)
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

Code:

from matplotlib import pyplot as plt
import numpy as np

import cv2

face_classifier = cv2.CascadeClassifier('haarcascades/haarcascade_frontalface_default.xml')


cap = cv2.VideoCapture(0)


# params for ShiTomasi corner detection
feature_params = dict( maxCorners = 200,
                       qualityLevel = 0.01,
                       minDistance = 10,
                       blockSize = 7 )

# Parameters for lucas kanade optical flow
lk_params = dict( winSize  = (15,15),
                  maxLevel = 2,
                  criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03))

# Create some random colors
color = np.random.randint(0,255,(100,3))

# Take first frame and find corners in it
ret, old_frame = cap.read()



cv2.imshow('Old_Frame', old_frame)
cv2.waitKey(0)
old_gray = cv2.cvtColor(old_frame, cv2.COLOR_BGR2GRAY)
restart = True
#while restart == True:
face = face_classifier.detectMultiScale(old_gray, 1.2, 4)

if len(face) == 0:
    print "This is empty"

for (x,y,w,h) in face:
    focused_face = old_frame[y: y+h, x: x+w]

cv2.imshow('Old_Frame', old_frame)

face_gray = cv2.cvtColor(old_frame,cv2.COLOR_BGR2GRAY)

gray = cv2.cvtColor(focused_face,cv2.COLOR_BGR2GRAY)

corners_t = cv2.goodFeaturesToTrack(gray, mask = None, **feature_params)
corners = np.int0(corners_t)

print corners

for i in corners:
    ix,iy = i.ravel()
    cv2.circle(focused_face,(ix,iy),3,255,-1)
    cv2.circle(old_frame,(x+ix,y+iy),3,255,-1)

plt.imshow(old_frame),plt.show()


# Create a mask image for drawing purposes
mask = np.zeros_like(old_frame)

while(1):
    ret,frame = cap.read()
    frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # calculate optical flow
    p1, st, err = cv2.calcOpticalFlowPyrLK(old_gray, frame_gray, corners_t, None, **lk_params)

    # Select good points
    good_new = p1[st==1]
    good_old = corners_t[st==1]

    # draw the tracks
    print "COLORING TIME!"
    for i,(new,old) in enumerate(zip(good_new,good_old)):
        print i
        print color[i]
        a,b = new.ravel()
        c,d = old.ravel()
        mask = cv2.line(mask, (a,b),(c,d), color[i].tolist(), 2)
        frame = cv2.circle(frame,(a, b),5,color[i].tolist(),-1)
        if i == 99:
            break
    img = cv2.add(frame,mask)

    cv2.imshow('frame',img)
    k = cv2.waitKey(30) & 0xff
    if k == 27:
        break

    # Now update the previous frame and previous points
    old_gray = frame_gray.copy()
    p0 = good_new.reshape(-1,1,2)

cv2.destroyAllWindows()
cap.release()

Answer 1

This error message

error: (-215)size.width>0 && size.height>0 in function imshow

simply means that imshow() is not getting video frame from input-device. You can try using

cap = cv2.VideoCapture(1) 

instead of

cap = cv2.VideoCapture(0) 

& see if the problem still persists.

Answer 2

I have the same problem, fix the ret in capture video

import numpy as np
import cv2

# Capture video from file
cap = cv2.VideoCapture('video1.avi')

while True:

    ret, frame = cap.read()

    if ret == True:

        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

        cv2.imshow('frame',gray)


        if cv2.waitKey(30) & 0xFF == ord('q'):
            break

    else:
        break

cap.release()
cv2.destroyAllWindows()

Answer 3

You have to delay

Example Code:

import cv2
import numpy as np
import time

cam = cv2.VideoCapture(0)
time.sleep(2)

while True:
    ret,frame = cam.read()
    cv2.imshow('webcam', frame)
    if cv2.waitKey(1)&0xFF == ord('q'):
        break

cam.release()
cv2.destroyAllWindows()

Answer 4

I also faced this problem and I solve it by changing the path of the image because if the path contains (for example: \n or \t or \a) it will make corruption so just change every back-slash "\" with front-slash "/" and it will not make any error only fix the issue of reading path

Answer 5

I have also met this issue. In my case, the image path is wrong, so the img read is NoneType. After I correct the image path, I can show it without any issue.

Answer 6

In these two lines:

mask = cv2.line(mask, (a,b),(c,d), color[i].tolist(), 2)

frame = cv2.circle(frame,(a, b),5,color[i].tolist(),-1)

try instead:

cv2.line(mask, (a,b),(c,d), color[i].tolist(), 2)

cv2.circle(frame,(a, b),5,color[i].tolist(),-1)

I had the same problem and the variables were being returned empty

Answer 7

while(cap.isOpened()):

    ret, img = cap.read()
    print img
    if img==None:   #termino los frames?
        break   #si, entonces terminar programa
    #gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    cv2.imshow('img2',img)

Answer 8

cv2.circle and cv2.lines are not working. Mask and frame both are returning None. these functions (line and circle) are in opencv 3 but not in older versions.

Answer 9

I use ssh to connect to remote server and have python code execute cv2.VideoCapture(0) to capture remote webcam, then encounter this error message:

error: (-215)size.width>0 && size.height>0 in function imshow

Finally, I have to grant access to /dev/video0 (which is my webcam device) with my user account and the error message was gone. Use usermod to add user into group video

usermod -a -G video user

Answer 10

I also met the error message in raspberry pi 3, but my solution is reload kernel of camera after search on google, hope it can help you.

sudo modprobe bcm2835-v4l2

BTW, for this error please check your camera and file path is workable or not

Answer 11

This is a problem with space consumption or choosing the wrong camera. My suggestion in to restart kernel and clear output and run it again. It works then.

Answer 12

Although this is an old thread, I got this error as well and the solution that worked for me is not mentioned here.

Simply put, in my case the webcam was still in use on the background, as I saw the LED light being on. I have not yet been able to reproduce the issue, so I'm not sure a simple cv2.VideoCapture(0).release() would have solved it. I'll edit this post if and when I have found it out.

For me a restart of my PC solved the issue, without changing anything to the code.

Answer 13

Check if you have "opencv_ffmpeg330.dll" in python27 root directory or of the python version you are using. If not you will find it in "....\OpenCV\opencv\build\bin".

Choose the appropriate version and copy the dll into the root directory of your python installation and re-run the program

Answer 14

Simply use an image extension like .jpeg or .png.