MOG Background Reduction OpenCV Python Tutorial

In this OpenCV with Python tutorial, we're going to be covering how to reduce the background of images, by detecting motion. This is going to require us to re-visit the use of video, or to have two images, one with the absense of people/objects you want to track, and another with the objects/people there. You can use your webcam if you like, or use a video like:

People walking sample video.

The code here is actually quite simple with what we know up to this point:

import numpy as np
import cv2

cap = cv2.VideoCapture('people-walking.mp4')
fgbg = cv2.createBackgroundSubtractorMOG2()

    ret, frame =

    fgmask = fgbg.apply(frame)

    k = cv2.waitKey(30) & 0xff
    if k == 27:



The idea here is to extract the moving forground from the static background. You can also use this to compare two similar images, and immediately extract the differences between them.

In our case, we can see we've definitely detected some people, but we do have some "noise" The noise is actually tree leaves moving a bit in the ambient wind. If only we knew of a way to diminish noise. Oh wait! we do! A wild challenge has appeared for you +=1 folks!

The next tutorial begins to move us away from applying filters or transforms and gets us detecting general objects using Haar Cascades for things like face detection and more.

The next tutorial:

  • OpenCV with Python Intro and loading Images tutorial
  • Loading Video Source OpenCV Python Tutorial
  • Drawing and Writing on Image OpenCV Python Tutorial
  • Image Operations OpenCV Python Tutorial
  • Image arithmetics and Logic OpenCV Python Tutorial
  • Thresholding OpenCV Python Tutorial
  • Color Filtering OpenCV Python Tutorial
  • Blurring and Smoothing OpenCV Python Tutorial
  • Morphological Transformations OpenCV Python Tutorial
  • Canny Edge Detection and Gradients OpenCV Python Tutorial
  • Template Matching OpenCV Python Tutorial
  • GrabCut Foreground Extraction OpenCV Python Tutorial
  • Corner Detection OpenCV Python Tutorial
  • Feature Matching (Homography) Brute Force OpenCV Python Tutorial
  • MOG Background Reduction OpenCV Python Tutorial
  • Haar Cascade Object Detection Face & Eye OpenCV Python Tutorial
  • Creating your own Haar Cascade OpenCV Python Tutorial