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Blue square not showing oh screen

asked 2015-01-18 18:06:24 -0500

Shaba1 gravatar image

updated 2015-01-20 22:29:19 -0500

berak gravatar image

Hello folk. I just started using opencv--python.

Intially I typed in some code found here.

link text

But when I typed in the code to my windows 7 64 bit computer and ran it. After a few syntax errors and typos on my part it ran just fine. I dectected the web camera that I have plugged in and it displayed the cameras video in a window. But I do not get that blue square that says it has detected my face. I am using a celron 2200 mhz with 2gb of ram so its not the fastest computer . Is it just that my computer is slow or is there something wrong with the code?

Ok here is the code. It was in the youtube video on the link that I posted,

import numpy as np
import cv2

#some comment i a foreign language which I cannot understand. I will put it
#thru Altavista later
face_cascade = cv2.CascadeClassifier('haarscascade_frontalface_default.xml')

video_capture = cv2.VideoCapture(0)

while True:
    ret, frame = video_capture.read()
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    #capture test with image.
    #img = cv2.imread("wyld2.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(frame,(x,y),(x+w,y+h),(255,0,0),2)  

    cv2.imshow('video', frame)
    #some more foreign comments
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
video_capture.release()
cv2.destroyAllWindows()
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Comments

Post your code.

boaz001 gravatar imageboaz001 ( 2015-01-19 02:28:33 -0500 )edit
2

without seeing anything of your stuff, i bet a beer, that it did not find the xml file for the cascade, because the path was wrong.

please try like: cv2.CascadeClassifier('complete/path/to/haarscascade_frontalface_default.xml')

berak gravatar imageberak ( 2015-01-20 21:41:07 -0500 )edit
1

it's most probably in opencv/data/haarcascades

also:

if face_cascade.empty(): raise Exception("cascade file not found !")
berak gravatar imageberak ( 2015-01-21 02:19:21 -0500 )edit

Like @berak said, 98% of cascade errors result from not reading correctly the model and not capturing the return value!

StevenPuttemans gravatar imageStevenPuttemans ( 2015-01-21 04:37:20 -0500 )edit

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answered 2015-01-21 21:14:20 -0500

Get the cascade and put it in the same directory.

wget https://jviolajones.googlecode.com/files/haarcascade_frontalface_default.xml

Now there was a typo in your code: haarScascade_frontalface_default.xml should be haarcascade_frontalface_default.xml

Change your code to this, make sure the indention is correct and it will work (make sure the cascade xml file is in the same directory):

import numpy as np
import cv2

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
video_capture = cv2.VideoCapture(0)

while True:
    ret, frame = video_capture.read()
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    faces = face_cascade.detectMultiScale(gray,1.3,5)
    for(x,y,w,h) in faces:
       cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)  
       print str(x)

   cv2.imshow('video', frame)
   if cv2.waitKey(1) & 0xFF == ord('q'):
     break
 video_capture.release()
 cv2.destroyAllWindows()

Tested with Python 2.7.6. This works on my machine. If that still does not work copy the code with static image face detection from here and see if that works.

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YES!!!! Finally something works :) I do not understand HOW it works or what it is doing but that is a goal for further study. Thanks you very much all those who took the time to answer.

Shaba1 gravatar imageShaba1 ( 2015-01-23 19:39:19 -0500 )edit
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Asked: 2015-01-18 18:06:24 -0500

Seen: 146 times

Last updated: Jan 21 '15