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 <module>
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?
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')
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 enter image description here
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
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")
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')
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.
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'
"\Anaconda3\Lib\site-packages\cv2\data\" I found the xml file in this path for Anaconda
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')"
no need to change the code
download that .xml file , then put the path of that file
it will solve the error (100%)
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
Your XML file was not found. Try using absolute paths like:
/path/to/my/file (Mac, Linux)
C:\\path\\to\\my\\file (Windows)
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) & 0xff
if k == 27:
break
cap.release()
cv2.destroyAllWindows()
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.
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.
来源：https://stackoverflow.com/questions/30508922/error-215-empty-in-function-detectmultiscale