%%?Face?Detection?and?Tracking?Using?the?KLT?Algorithm
%?This?example?shows?how?to?automatically?detect?and?track?a?face?using
%?feature?points.?The?approach?in?this?example?keeps?track?of?the?face?even
%?when?the?person?tilts?his?or?her?head?or?moves?toward?or?away?from?the
%?camera.
%
%???Copyright?2013?The?MathWorks?Inc.

%%?Detect?a?Face
%?Create?a?cascade?detector?object.
faceDetector?=?vision.CascadeobjectDetector（）;

%?Open?a?video?file
videoFileReader?=?vision.VideoFileReader（‘tilted_face.avi‘）;

%?Read?a?video?frame?and?run?the?face?detector.
videoframe??????=?step（videoFileReader）;
bbox????????????=?step（faceDetector?videoframe）;

%?Convert?the?box?to?a?polygon.?This?is?needed?to?be?able?to?visualize?the
%?rotation?of?the?object.
x?=?bbox（1）;?y?=?bbox（2）;?w?=?bbox（3）;?h?=?bbox（4）;
bboxPolygon?=?[x?y?x+w?y?x+w?y+h?x?y+h];

%?Draw?the?returned?bounding?box?around?the?detected?face.
shapeInserter??=?vision.ShapeInserter（‘Shape‘?‘Polygons‘?‘BorderColor‘‘Custom‘...
????‘CustomBorderColor‘[255?255?0]）;
videoframe?=?step（shapeInserter?videoframe?bboxPolygon）;
figure;?imshow（videoframe）;?title（‘Detected?face‘）;

%%?Identify?Facial?Features?To?Track
%?Crop?out?the?region?of?the?image?containing?the?face?and?detect?the
%?feature?points?inside?it.
cornerDetector?=?vision.CornerDetector（‘Method‘?...
????‘Minimum?eigenvalue?（Shi?&?Tomasi）‘）;
points?=?step（cornerDetector?rgb2gray（imcrop（videoframe?bbox）））;

%?The?coordinates?of?the?feature?points?are?with?respect?to?the?cropped?
%?region.?They?need?to?be?translated?back?into?the?original?image
%?coordinate?system.?
points?=?double（points）;
points（:?1）?=?points（:?1）?+?double（bbox（1））;
points（:?2）?=?points（:?2）?+?double（bbox（2））;

%?Display?the?detected?points.
markerInserter?=?vision.MarkerInserter（‘Shape‘?‘Plus‘?...
????‘BorderColor‘?‘White‘）;
videoframe?=?step（markerInserter?videoframe?points）;
figure?imshow（videoframe）?title（‘Detected?features‘）;

%%?Initialize?a?Tracker?to?Track?the?Points
%?Create?a?point?tracker?and?enable?the?bidirectional?error?constraint?to
%?make?it?more?robust?in?the?presence?of?noise?and?clutter.
pointTracker?=?vision.PointTracker（‘MaxBidirectionalError‘?2）;

%?Initialize?the?tracker?with?the?initial?point?locations?and?the?initial
%?vide