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  lt module gt  cv2 imshow  frame  img  error   build buildd opencv-2 4 8 dfsg1 modules highgui src window cpp 269   error   -215 size width gt 0  amp  amp  size height gt 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   amp  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

User · Answer

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

User · Answer

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  amp  amp  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

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This Error can also occur if you slice a negative point and pass it to the array  So check if you did

User · Answer

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  amp 0xFF    ord  q            break  cam release   cv2 destroyAllWindows

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Simply use an image extension like  jpeg or  png

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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   amp  0xFF    ord  q                break      else          break  cap release   cv2 destroyAllWindows

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

This error message      error   -215 size width 0  amp  amp  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      amp  see if the problem still persists

User · Answer

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

User · Answer

I had this problem  Solution  Update the path of the image  If the path contains  for example   n or  t or  a  it adds to the corruption  Therefore  change every back-slash  quot   quot  with front-slash  quot   quot  and it will not make create error but fix the issue of reading path  Also double check the file path name  any typo in the name or path also gives the same error

User · Answer

I was facing the same problem while trying to open images containing spaces and special characters like the following    So  after modifying the images names removing their spaces and special characters  everything worked perfectly

User · Answer

That error also shows when the video has played fine and the script will finish but that error always throws because the imshow   will get empty frames after all frames have been consumed    That is especially the case if you are playing a short  few sec  video file and you don t notice that the video actually played on the background  behind your code editor  and after that the script ends with that error

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

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