Building Computer Vision Projects with OpenCV 4 and C++

Detecting the face

Now that we have converted the image to grayscale, shrunk the image, and equalized the histogram, we are ready to detect the faces using the CascadeClassifier::detectMultiScale() function! There are many parameters, listed as follows, that we pass to this function:

• minFeatureSize: This parameter determines the minimum face size that we care about, typically 20 x 20 or 30 x 30 pixels, but this depends on your use case and image size. If you are performing face detection on a webcam or smartphone where the face will always be very close to the camera, you could enlarge this to 80 x 80 to have much faster detection, or if you want to detect far away faces, such as on a beach with friends, then leave this as 20 x 20.
• searchScaleFactor ...