SimpleCV camera feed unreliable

Question

When I try to use the camera approximately 2/3rds of the time it doesn't work, just shows a black screen, however the other 1/3rd of the time it does work and shows an image.

from SimpleCV import *

cam = Camera()
disp = Display()
findFace = HaarCascade("face")

while disp.isNotDone():
    img = cam.getImage()
    face = img.findHaarFeatures(findFace)
    if face:
        face.draw()
        bb = face[-1].boundingBox()
        txt1 = str(bb[0])
        txt2 = str(bb[1])
        txt3 = str(bb[2])
        txt4 = str(bb[3])
        text = txt1+" "+txt2+" "+txt3+" "+txt4
        img.drawText(text)
    img.save(disp)

I've tried other codes and it always does this to me. I also know my webcam is on, as the light for it is on.

When I close the image window it throws these errors, though it's only when I close it

Traceback (most recent call last):
  File "C:/Python27/MyTryFace", line 7, in <module>
    while disp.isNotDone():
  File "C:\Python27\lib\site-packages\SimpleCV\Display.py", line 672, in isNotDone
    return not self.isDone()
  File "C:\Python27\lib\site-packages\SimpleCV\Display.py", line 650, in isDone
    self.checkEvents()
  File "C:\Python27\lib\site-packages\SimpleCV\Display.py", line 615, in checkEvents
    pressed = pg.key.get_pressed()
error: video system not initialized

Answer 1

我发现在while循环开始之前添加img = cam.getImage()会解决我的不可靠性问题。 （这也将在while循环中再次出现）