Create a detector object.

faceDetector = vision.CascadeObjectDetector;

Read input image.

I = imread('visionteam.jpg');

Detect faces.

bboxes = step(faceDetector, I);

Annotate detected faces.

IFaces = insertObjectAnnotation(I, 'rectangle', bboxes, 'Face');

figure, imshow(IFaces), title('Detected faces');