error: (-215:Assertion failed) ! Empty() in Function 'detectMultiScale'

Question

I’m totally layy on linux and I’m trying to use opencv version 3.4.2 with python 3.5.2 on linux Mint to run an example facial detection code. Below the code:

import numpy as np
import cv2

classificador = cv2.CascadeClassifier('\home\linux\Documentos\deteccao\haarcascade_frontalface_default.xml')

imagem = cv2.imread('pessoas.jpg')
imagemCinza = cv2.cvtColor(imagem, cv2.COLOR_BGR2GRAY)

facesDetectadas = classificador.detectMultiScale(imagemCinza, scaleFactor=1.1, minNeighbors=20, minSize=(30,30))
print(len(facesDetectadas))
print(facesDetectadas)

for (x, y, l, a) in facesDetectadas:
print(x, y, l, a)
cv2.rectangle(imagem, (x, y), (x + l, y + a), (255, 0, 255), 2)

cv2.imshow("Faces encontradas", imagem)
cv2.waitKey()

And down here, the mistake:

Traceback (most recent call last):
 File "exemplo1.py", line 11, in <module>
  facesDetectadas = classificador.detectMultiScale(imagemCinza, scaleFactor=1.1, minNeighbors=20, minSize=(30,30))
cv2.error: OpenCV(3.4.2) /io/opencv/modules/objdetect/src/cascadedetect.cpp:1698: error: (-215:Assertion failed) !empty() in function 'detectMultiScale'

Answer 1

The mistake was on that line:

classificador = cv2.CascadeClassifier('\home\linux\Documentos\deteccao\haarcascade_frontalface_default.xml')

The correct bar to use:

classificador = cv2.CascadeClassifier('/home/linux/Documentos/deteccao/haarcascade_frontalface_default.xml')