Chapter 5. Motion Detection

In this chapter, we plan to extend the interactivity beyond the use of mouse and keyboard. Motion detection needs the computer webcam to capture and detect the body movement of users. In Chapter 3, Image Processing, we worked with the pix_video object to obtain the live video stream. So far, we only displayed the video or applied effects on it. We have no idea about what is happening within the video image. In the coming sections, we try to make sense of the image.

In a video frame, all we know is the width, height of the frame, the number of pixels, and the red, green, and blue color components of each pixel. We have no idea whether there is a bird or pig in the frame. And we do not know whether the subject in the video frame is moving or not. In order to identify movement, we have to compare a frame with another reference frame. The following sections will introduce a number of topics including:

• Obtaining the frame difference

• Detecting presence

• Detecting motion

• Creating...