Python face detection error with opencv

Question

I try to use python face detection software. But when I launch it i recive this error:

OpenCV Error: Unspecified error (The node does not represent a user object (unknown type?)) in cvRead, file /build/opencv-FWWjHr/opencv-2.4.9.1+dfsg/modules/core/src/persistence.cpp, line 4991
Traceback (most recent call last):
  File "riconoscimentofacciale.py", line 57, in <module>
    faceCascade = cv.Load("haarcascade_frontalface_default.xml")
cv2.error: The node does not represent a user object (unknown type?)

the source code is this:

#!/usr/bin/python

import cv
import cv2
import time
import Image

def DetectFace(image, faceCascade):

    min_size = (20,20)
    image_scale = 2
    haar_scale = 1.1
    min_neighbors = 3
    haar_flags = 0

    # Allocate the temporary images
    grayscale = cv.CreateImage((image.width, image.height), 8, 1)
    smallImage = cv.CreateImage(
            (
                cv.Round(image.width / image_scale),
                cv.Round(image.height / image_scale)
            ), 8 ,1)

    # Convert color input image to grayscale
    cv.CvtColor(image, grayscale, cv.CV_BGR2GRAY)

    # Scale input image for faster processing
    cv.Resize(grayscale, smallImage, cv.CV_INTER_LINEAR)

    # Equalize the histogram
    cv.EqualizeHist(smallImage, smallImage)

    # Detect the faces
    faces = cv.HaarDetectObjects(
            smallImage, faceCascade, cv.CreateMemStorage(0),
            haar_scale, min_neighbors, haar_flags, min_size
        )

    # If faces are found
    if faces:
        for ((x, y, w, h), n) in faces:
            # the input to cv.HaarDetectObjects was resized, so scale the
            # bounding box of each face and convert it to two CvPoints
            pt1 = (int(x * image_scale), int(y * image_scale))
            pt2 = (int((x + w) * image_scale), int((y + h) * image_scale))
            cv.Rectangle(image, pt1, pt2, cv.RGB(255, 0, 0), 5, 8, 0)

    return image

#----------
# M A I N
#----------

capture = cv.CaptureFromCAM(0)
#capture = cv.CaptureFromFile("test.avi")

faceCascade = cv.Load("haarcascade_frontalface_default.xml")
#faceCascade = cv.Load("haarcascades/haarcascade_frontalface_alt2.xml")
#faceCascade = cv.Load("haarcascades/haarcascade_frontalface_alt.xml")
#faceCascade = cv.Load("haarcascades/haarcascade_frontalface_alt_tree.xml")

while (cv.WaitKey(15)==-1):
    img = cv.QueryFrame(capture)
    image = DetectFace(img, faceCascade)
    cv.ShowImage("face detection test", image)

cv.ReleaseCapture(capture)

I have set-up all right, I followed guide

I download all, install all, create and put the right file/drectory. But still face the error.

please use the cv2 api, not the deprecated cv one (which is gone in opencv3) also see sample — berak
– berak, Commented Nov 13, 2015 at 14:20
For Face Detection i.e. If its Obama's face or Trumps in real time check out the source code of this GitHub Repo github.com/UBISOFT-1/Project_Exodus.git — Muneeb Ahmad Khurram
– Muneeb Ahmad Khurram, Commented May 25, 2021 at 18:47

Abhishek · Accepted Answer · 2016-02-01 16:40:49Z

5

One of the most common error new developer faces here is old code which refers to old xml file.

Download this haarcascade_frontalface_alt.xml xml file and replace

faceCascade = cv.Load("haarcascade_frontalface_default.xml")

with

faceCascade = cv.Load("Complete_path_of_THiS_NEW_File")

if you downlaoded the file in downloadfolder then

faceCascade = cv.Load("/home/webadmin/Downloads/haarcascade_frontalface_default.xml")

Hope this helps

answered Feb 1, 2016 at 16:40

Abhishek

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1 Comment

Carlo Zanocco Over a year ago

Thanks! That solved the problem! I followed your step and now is all working

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