setup

% Create the face detector object. faceDetector = vision.CascadeObjectDetector(); % Create the point tracker object. pointTracker = vision.PointTracker('MaxBidirectionalError', 2); % Create the webcam object. cam = webcam(); % Capture one frame to get its size. videoFrame = snapshot(cam); frameSize = size(videoFrame); % Create the video player object. videoPlayer = vision.VideoPlayer('Position', [100 100 [frameSize(2), frameSize(1)]+30]);

Detection and Tracking

runLoop = true; numPts = 0; frameCount = 0; while runLoop && frameCount < 400 % Get the next frame. videoFrame = snapshot(cam); videoFrameGray = rgb2gray(videoFrame); frameCount = frameCount + 1; if numPts < 10 % Detection mode. bbox = faceDetector.step(videoFrameGray); if ~isempty(bbox) % Find corner points inside the detected region. points = detectMinEigenFeatures(videoFrameGray, 'ROI', bbox(1, :)); % Re-initialize the point tracker. xyPoints = points.Location; numPts = size(xyPoints,1); release(pointTracker); initialize(pointTracker, xyPoints, videoFrameGray); % Save a copy of the points. oldPoints = xyPoints; % Convert the rectangle represented as [x, y, w, h] into an % M-by-2 matrix of [x,y] coordinates of the four corners. This % is needed to be able to transform the bounding box to display % the orientation of the face. bboxPoints = bbox2points(bbox(1, :)); % Convert the box corners into the [x1 y1 x2 y2 x3 y3 x4 y4] % format required by insertShape. bboxPolygon = reshape(bboxPoints', 1, []); % Display a bounding box around the detected face. videoFrame = insertShape(videoFrame, 'Polygon', bboxPolygon, 'LineWidth', 3); % Display detected corners. videoFrame = insertMarker(videoFrame, xyPoints, '+', 'Color', 'white'); end else % Tracking mode. [xyPoints, isFound] = step(pointTracker, videoFrameGray); visiblePoints = xyPoints(isFound, :); oldInliers = oldPoints(isFound, :); numPts = size(visiblePoints, 1); if numPts >= 10 % Estimate the geometric transformation between the old points % and the new points. [xform, oldInliers, visiblePoints] = estimateGeometricTransform(... oldInliers, visiblePoints, 'similarity', 'MaxDistance', 4); % Apply the transformation to the bounding box. bboxPoints = transformPointsForward(xform, bboxPoints); % Convert the box corners into the [x1 y1 x2 y2 x3 y3 x4 y4] % format required by insertShape. bboxPolygon = reshape(bboxPoints', 1, []); % Display a bounding box around the face being tracked. videoFrame = insertShape(videoFrame, 'Polygon', bboxPolygon, 'LineWidth', 3); % Display tracked points. videoFrame = insertMarker(videoFrame, visiblePoints, '+', 'Color', 'white'); % Reset the points. oldPoints = visiblePoints; setPoints(pointTracker, oldPoints); end end % Display the annotated video frame using the video player object. step(videoPlayer, videoFrame); % Check whether the video player window has been closed. runLoop = isOpen(videoPlayer); end % Clean up. clear cam; release(videoPlayer); release(pointTracker); release(faceDetector);

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I need an explanation of every single line of this MATLAB code, please...