Catalin George Festila: OpenGL and OpenCV with python 2.7 - part 002.

I deal today with opencv and I fix some of my errors.
One is this error I got with cv2.VideoCapture. When I  try to used with load video and createBackgroundSubtractorMOG2() i got this:

cv2.error:   C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\highgui\src\window.cpp:281:  error: (-215) size.width0 amp="" cv::imshow="" function="" i="" in="" size.height="">
You need also to have opencv_ffmpeg310.dll and opencv_ffmpeg310_64.dll into your Windows C:\Windows\System32, this will help me to play videos.
Now make sure you have the opencv version 3.1.0 because opencv come with some changes over python.
C:\Python27\python
Python 2.7.8 (default, Jun 30 2014, 16:08:48) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>import cv2
>>>print cv2.__version__
3.1.0

You can take some infos from about opencv python module - cv2 with:

>>>cv2.getBuildInformation()
...
>>>cv2.getCPUTickCount()
...
>>>print cv2.getNumberOfCPUs()
...
>>>print cv2.ocl.haveOpenCL()
True

You can also see some error by disable OpenCL:

>>>cv2.ocl.setUseOpenCL(False)
>>>print cv2.ocl.useOpenCL()
False

Now will show you how to use webcam gray and color , and play one video:
webcam color

import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
    ret, frame = cap.read()
    cv2.imshow('frame',frame)
    if 0xFF & cv2.waitKey(5) == 27:
        break
cap.release()
cv2.destroyAllWindows()

webcam gray

import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
    ret, frame = cap.read()
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imshow('frame',gray)
    if 0xFF & cv2.waitKey(5) == 27:
        break
cap.release()
cv2.destroyAllWindows()

play video

import cv2
from cv2 import *
capture = cv2.VideoCapture("avi_test_001.avi")
while True:
    ret, img = capture.read()
    cv2.imshow('some', img)
    if 0xFF & cv2.waitKey(5) == 27:
        break
cv2.destroyAllWindows()