问题
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?
回答1:
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')
回答2:
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
回答3:
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
回答4:
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")
回答5:
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')
回答6:
no need to change the code
download that .xml file , then put the path of that file
it will solve the error (100%)
回答7:
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.
回答8:
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'
回答9:
"\Anaconda3\Lib\site-packages\cv2\data\" I found the xml file in this path for Anaconda
回答10:
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')"
回答11:
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
回答12:
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.
回答13:
Your XML file was not found. Try using absolute paths like:
/path/to/my/file (Mac, Linux)
C:\\path\\to\\my\\file (Windows)
回答14:
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()
回答15:
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.
回答16:
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!
来源：https://stackoverflow.com/questions/30508922/error-215-empty-in-function-detectmultiscale