error -215 empty in function detectMultiScale

Question

I m trying to learn cv2 in python 2 7  but when I run my code  in the specific part of it   face cascade   cv2 CascadeClassifier  haarcascade frontalface default xml    eye cascade   cv2 CascadeClassifier  haarcascade eye xml     img   cv2 imread  2015-05-27-191152 jpg   gray   cv2 cvtColor img  cv2 COLOR BGR2GRAY   faces   face cascade detectMultiScale gray  1 3  5  for  x y w h  in faces      img   cv2 rectangle img  x y   x w y h   255 0 0  2    it returns this   File  face detection py   line 11  in  lt module gt      faces   face cascade detectMultiScale gray  1 3  5  cv2 error   home arthurckl Desktop opencv-3 0 0-rc1 modules objdetect src cascadedetect cpp 1595  error   -215   empty   in function detectMultiScale   I tried to search the answer here but the best i could find is that I must be loading the face cascade the wrong way    Any help

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Anaconda3 Lib site-packages cv2 data   I found the xml file in this path for Anaconda

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the error may be due to  the required xml files has not been loaded properly  Search for the file haarcascade frontalface default xml  by using the search engine of ur OS get the full path and put it as the argument to cv2 CascadeClassifier as string

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no need to change the code   download that  xml file   then put the path of that file   it will solve the error  100

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You may find such kind of errors when you did not define the complete path of your XML file  Try this one if you are using opencv3 1 0 in raspberrypi 3   faceCascade   cv2 CascadeClassifier   home pi opencv-3 1 0 data haarcascades haarcascade frontalface default xml

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I found this in some other answer but eventually worked for me when I added the two answers  import cv2 from matplotlib import pyplot as plt import numpy as np face cascade   cv2 CascadeClassifier cv2 data haarcascades    quot haarcascade frontalface default xml quot   eye cascade   cv2 CascadeClassifier cv2 data haarcascades    quot haarcascade eye xml quot    img   cv2 imread  image1 jpg   gray   cv2 cvtColor img  cv2 COLOR BGR2GRAY  faces   face cascade detectMultiScale gray  1 3  5

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On OSX with a homebrew install the full path to the opencv folder should work   face cascade   cv2 CascadeClassifier   usr local Cellar opencv 3 4 0 1 share OpenCV haarcascades haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier   usr local Cellar opencv 3 4 0 1 share OpenCV haarcascades haarcascade eye xml     Take care of the version number in the path

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You can solve this problem by placing XML in the same directory in which your main python file  from where you tried to include this file  was placed  Now the next step is to use full path  For example  This will not work  front cascade   cv2 CascadeClassifier    haarcascade eye xml     Use full path  now it will work fine  front cascade   cv2 CascadeClassifier   Users xyz Documents project haarcascade eye xml

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I had the same issue   I didn t need to download anything else to solve this  CV2 had everything I needed    Instead of trying to figure out where the  xml files are and hard coding the values  I used a property given by cv2    From OP  face cascade   cv2 CascadeClassifier  haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier  haarcascade eye xml     Becomes   face cascade   cv2 CascadeClassifier cv2 data haarcascades    haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier cv2 data haarcascades    haarcascade eye xml

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Probably the face cascade is empty  You can check if the variable is empty or not by typing following command   face cascade empty     If it is empty you will get True and this means your file is not available in the path you mentioned   Try to add complete path of xml file as follows   r D  folder Name haarcascade frontalface default xml

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The main idea of the solution as above mentioned  find the right path of the  xml file and use it to access the file correctly  In my case  I installed the opencv in anoconda env  first direct to path of Anoconda  then  find the path of  xml file by using    find   -name  haarcascade eye xml    for example search the haarcascade eye xml file in current dir       Then use the return path    eye cascade   cv2 CascadeClassifier path    haarcascade eye xml

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The error occurs due to missing of xml files or incorrect path of xml file    Please try the following code   import numpy as np import cv2  face cascade   cv2 CascadeClassifier  haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier  haarcascade eye xml    cap   cv2 VideoCapture 0   while 1      ret  img   cap read       gray   cv2 cvtColor img  cv2 COLOR BGR2GRAY      faces   face cascade detectMultiScale gray  1 3  5       for  x y w h  in faces          cv2 rectangle img  x y   x w y h   255 0 0  2          roi gray   gray y y h  x x w          roi color   img y y h  x x w           eyes   eye cascade detectMultiScale roi gray          for  ex ey ew eh  in eyes              cv2 rectangle roi color  ex ey   ex ew ey eh   0 255 0  2       cv2 imshow  img  img      k   cv2 waitKey 30   amp  0xff     if k    27          break  cap release   cv2 destroyAllWindows

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Use the entire file path and use      instead of     in the xml file path   The file path should be as follows   face cascade   cv2 CascadeClassifier  C   opencv  build  etc  haarcascades  haarcascade frontalface default xml     instead of    cascade fn   args get  --cascade          data haarcascades haarcascade frontalface alt xml

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If you are using Anaconda you should add the Anaconda path   new path    C  Users     Anaconda Library etc haarcascades    face cascade   cv2 CascadeClassifier new path    haarcascade frontalface default xml

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I had the same problem with opencv-python and I used a virtual environment  If it s your case  you should find the xml files at    home username virtual environment lib python3 5 site-packages cv2 data haarcascade frontalface default xml   home username virtual environment lib python3 5 site-packages cv2 data haarcascade eye xml  Please be sure that you re using the absolute path  Otherwise  it won t work

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I ran the same code  There are two things to note here  1  Give the entire path of the  xml files  2  Give a key press event instruction at the end   Add this block of code at the end and run your file  worked for me   k   cv2 waitKey 0  if k    27            wait for ESC key to exit     cv2 destroyAllWindows   elif k    ord  s      wait for  s  key to save and exit     cv2 imwrite  messigray png  img      cv2 destroyAllWindows     For example  my code looked like   import numpy as np import cv2  face cascade   cv2 CascadeClassifier  C   opencv  build  etc  haarcascades  haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier  C   opencv  build  etc  haarcascades  haarcascade eye xml    img   cv2 imread  lena jpg    gray   cv2 cvtColor img  cv2 COLOR BGR2GRAY   faces   face cascade detectMultiScale gray  1 3  5   faces   face cascade detectMultiScale gray   for  x y w h  in faces      cv2 rectangle img  x y   x w y h   255 0 0  2      roi gray   gray y y h  x x w      roi color   img y y h  x x w      eyes   eye cascade detectMultiScale roi gray      for  ex ey ew eh  in eyes          cv2 rectangle roi color  ex ey   ex ew ey eh   0 255 0  2   cv2 imshow  img  img   k   cv2 waitKey 0  if k    27            wait for ESC key to exit     cv2 destroyAllWindows   elif k    ord  s      wait for  s  key to save and exit     cv2 imwrite  messigray png  img      cv2 destroyAllWindows     My output looked like this

User · Answer

The XML file is missing  you can get the file from the GitHub repository and place it in the same directory as your project  Link to the folder on GitHub is here  Just download the file named haarcascade frontalface default xml  Actually  the file exists on your system  Just go to the site-packages folder of your python installation folder and check the cv2 data folder for the file

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Your XML file was not found  Try using absolute paths like    path to my file  Mac  Linux  C   path  to  my  file  Windows

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I ran into the same problem  but wrote the correct location   face cascade   cv2 CascadeClassifier    model haarcascade frontalface default xml     I figured out that i need to declare the full path to remove the error   face cascade   cv2 CascadeClassifier  C  pythonScript Facial-Emotion-Detection model haarcascade frontalface default xml

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This error means that the XML file could not be found  The library needs you to pass it the full path  even though you   re probably just using a file that came with the OpenCV library   You can use the built-in pkg resources module to automatically determine this for you  The following code looks up the full path to a file inside wherever the cv2 module was loaded from   import pkg resources haar xml   pkg resources resource filename       cv2    data haarcascade frontalface default xml     For me this was   Users andrew  local share virtualenvs foo- b9W43ee lib python3 7 site-packages cv2 data haarcascade frontalface default xml   yours is guaranteed to be different  Just let python   s pkg resources library figure it out   classifier   cv2 CascadeClassifier haar xml  faces   classifier detectMultiScale frame    Success

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The XML or file is missing or the path to it is incorrect or the create capture path is incorrect   The paths in the opencv sample look like this   cascade fn   args get  --cascade          data haarcascades haarcascade frontalface alt xml   nested fn    args get  --nested-cascade          data haarcascades haarcascade eye xml    cam   create capture video src  fallback  synth bg    data lena jpg noise 0 05

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I faced a similar issue  It seems correcting the path to XML makes this error to go away

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Please do not copy paste the content of xml file  because once you paste it to notepad it will be saved a s text file  So directly download the file from the given source

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You just need to add proper path of the haarcascade frontalface default xml file i e  you only have to add prefix  cv2 data haarcascades  face cascade   cv2 CascadeClassifier cv2 data haarcascades    haarcascade frontalface default xml   eye cascade   cv2 CascadeClassifier cv2 data haarcascades    haarcascade eye xml

[python] error: (-215) !empty() in function detectMultiScale

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