Overlaying A Facemask

        // Capture the current frame

        cap >> frame;

        // Resize the frame

        resize(frame, frame, Size(), scalingFactor, scalingFactor, INTER_AREA);

        // Convert to grayscale

        cvtColor(frame, frameGray, CV_BGR2GRAY);

        // Equalize the histogram

        equalizeHist(frameGray, frameGray);

        // Detect faces

        faceCascade.detectMultiScale(frameGray, faces, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE, Size(30, 30) );

        // Draw green rectangle around the face

        for(int i = 0; i < faces.size(); i++)

        {

            //Rect faceRect(faces[i].x, faces[i].y, faces[i].width, faces[i].height);

            // Custom parameters to make the mask fit your face. You may have to play around with them to make sure it works.

            int x = faces[i].x - int(0.1*faces[i].width);

            int y = faces[i].y - int(0.1*faces[i].height); // 0.0*faces[i].height

            int w = int(1.1 * faces[i].width);

            int h = int(1.3 * faces[i].height);

            // Extract region of interest (ROI) covering your face

            frameROI = frame(Rect(x,y,w,h));

            // Resize the face mask image based on the dimensions of the above ROI

            resize(faceMask, faceMaskSmall, Size(w,h));

            // Convert the above image to grayscale

            cvtColor(faceMaskSmall, grayMaskSmall, CV_BGR2GRAY);

            // Threshold the above image to isolate the pixels associated only with the face mask

            threshold(grayMaskSmall, grayMaskSmallThresh, 230, 255, CV_THRESH_BINARY_INV);

            // Create mask by inverting the above image (because we don't want the background to affect the overlay)

            bitwise_not(grayMaskSmallThresh, grayMaskSmallThreshInv);

            // Use bitwise "AND" operator to extract precise boundary of face mask

            bitwise_and(faceMaskSmall, faceMaskSmall, maskedFace, grayMaskSmallThresh);

            // Use bitwise "AND" operator to overlay face mask

            bitwise_and(frameROI, frameROI, maskedFrame, grayMaskSmallThreshInv);

            // Add the above masked images and place it in the original frame ROI to create the final image

            add(maskedFace, maskedFrame, frame(Rect(x,y,w,h)));

        }