CODEWITHSUNDEEP
pythonopencvcomputer-visionface-detection
praddy26
praddy26

Reputation: 105

Face detection throws error: !empty() in function cv::CascadeClassifier::detectMultiScale

I am using the inbuilt cascade classifier for the face detection. This is how the code is (OpenCV Python Tutorials):

import numpy as np
import cv2

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')

img = cv2.imread('ammma.jpg')
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)
cv2.waitKey(0)
cv2.destroyAllWindows()

But when I run the code I am getting the following error:

C:\Python27\python.exe C:/Users/DELL/Downloads/Amma/code/fd.py

OpenCV Error: Assertion failed (!empty()) in cv::CascadeClassifier::detectMultiScale, file C:\builds\master_PackSlaveAddon-win32-vc12-static\opencv\modules\objdetect\src\cascadedetect.cpp, line 1634 Traceback (most recent call last): File "C:/Users/DELL/Downloads/Amma/code/fd.py", line 10, in faces = face_cascade.detectMultiScale(img, 1.3, 5) cv2.error: C:\builds\master_PackSlaveAddon-win32-vc12-static\opencv\modules\objdetect\src\cascadedetect.cpp:1634: error: (-215) !empty() in function cv::CascadeClassifier::detectMultiScale

Upvotes: 8

Views: 57046

Answers (9)

Kiteretsu
Kiteretsu

Reputation: 3

https://github.com/udacity/P1_Facial_Keypoints/issues/13#issuecomment-385461579

After following the following comment. In you jupyter lab, open the kernel from the options where 'File', 'Edit', 'View', etc. Now choose, 'Change Kernel' and select 'Python [conda env:root]'.

Do this and you are done.

Upvotes: 0

Ajinkya Gholape
Ajinkya Gholape

Reputation: 11

In newer versions of opencv haarcascades also gets installed you just need the file location of haarcascades, to get it you can use cv2.data.haarcascades just like shown below

cascPath = "haarcascade_frontalface_default.xml"
faceCascade = cv2.CascadeClassifier(cv2.data.haarcascades + cascPath)

Upvotes: 0

Yerry Aguirre
Yerry Aguirre

Reputation: 101

Maybe, you use virtualenv for python like me. You try this.

import os

base_directory = os.path.abspath(os.getcwd())
directory_cv2 = os.path.join(base_directory, "Lib", "site-packages", "cv2","data")
print("la carpeta es: {}".format(directory_cv2))

Upvotes: 0

Sarvavyapi
Sarvavyapi

Reputation: 850

This post is old, but here is my answer nevertheless. Using absolute path did not work. Turns out that the XML file that I had downloaded (using curl) was corrupt. I had to manually copy and paste the contents from the github folder after which everything started working. Zhanwen Chen's answer also works (which I believe is the right way to do it for in-built classifiers).

Upvotes: 0

Zhanwen Chen
Zhanwen Chen

Reputation: 1463

You do NOT need to download or copy the .xml files. According to the OpenCV-Python PyPi page, you can simply use the packaged path to the installed cascades - cv2.data.haarcascades:

import cv2

# Globals
FACE_CLASSIFIER = cv2.CascadeClassifier(cv2.data.haarcascades + 'haarcascade_frontalface_default.xml')
EYE_CLASSIFIER = cv2.CascadeClassifier(cv2.data.haarcascades + 'haarcascade_eye.xml')
SCALE_FACTOR = 1.3
BLUE_COLOR = (255, 0, 0)
MIN_NEIGHBORS = 5

# Then use it however you'd like
try:
    faces = FACE_CLASSIFIER.detectMultiScale(gray, SCALE_FACTOR, MIN_NEIGHBORS)
    for (x, y, w, h) in faces:
        cv2.rectangle(self.roi_frame, (x, y), (x+w, y+h), BLUE_COLOR, HAAR_LINE_THICKNESS)
        roi_gray = gray[y:y+h, x:x+w]
        roi_color = self.roi_frame[y:y+h, x:x+w]
        eyes = EYE_CLASSIFIER.detectMultiScale(roi_gray)
        for (ex, ey, ew, eh) in eyes:
            cv2.rectangle(roi_color, (ex, ey), (ex+ew, ey+eh), GREEN_COLOR, HAAR_LINE_THICKNESS)
except Exception as e:
    warnings.warn('{}.show_haar_features: got exception {}'.format(__name__, e))

Upvotes: 12

Vakkalagadda Tarun
Vakkalagadda Tarun

Reputation: 33

I faced the same problem. First you will have to give the correct path of the file to the system, which looks like this: /home/xxxx/Desktop/Projects/haarcascade_eye.xml. Next, you'll have to open the code on github and save the raw version of the code for it run. It's advisable for both the files to be in the folder where you are storing your project file. Happy coding

Upvotes: 1

Shashank tiwari
Shashank tiwari

Reputation: 27

Well If you are getting this error then you need to download those 2 .xml files, because python can't find them on pc. I had same problem, then I downloaded the .xml files and kept it in folder where my .py file is. and then I got the perfect output. For downloading the files, search the file name and download it from sourceforge.

Upvotes: 0

SBhandari
SBhandari

Reputation: 21

I just happened to see this post when I faced a similar issue. I successfully resolved the error by executing the below 2 lines:

face_cascade = cv2.CascadeClassifier('opencv-3.0.0/data/harcascades/haarcascade_frontalface.xml')

eye_cascade = cv2.CascadeClassifier('opencv-3.0.0/data/harcascades/haarcascade_eye.xml')

Maybe, it will help others in resolving the same!

Upvotes: 2

akarsakov
akarsakov

Reputation: 2154

Refer to this line of code, it failed on checking that cascade is non empty. Please check path to XML files with trained cascades. You may need to specify full path to XML's like this:

face_cascade = cv2.CascadeClassifier('D:\opencv\data\haarcascades\haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('D:\opencv\data\haarcascades\haarcascade_eye.xml')

Or just put this files to directory containig your script.

Upvotes: 32

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