Building Computer Vision Projects with OpenCV 4 and C++

Accessing the webcam

To access a computer's webcam or camera device, you can simply call the open() function on a cv::VideoCapture object (OpenCV's method of accessing your camera device), and pass 0 as the default camera ID number. Some computers have multiple cameras attached, or they do not work with a default camera of 0, so it is common practice to allow the user to pass the desired camera number as a command-line argument, in case they want to try camera 1, 2, or -1, for example. We will also try to set the camera resolution to 640 x 480 using cv::VideoCapture::set() to run faster on high-resolution cameras.

Depending on your camera model, driver, or system, OpenCV might not change the properties of your camera. It is not important ...