I propose you to draw a rectangle of the BoundingBox and lines between Landmarks

[TibGva]

http://docs.aws.amazon.com/fr_fr/rekognition/latest/dg/API_BoundingBox.html
http://docs.aws.amazon.com/fr_fr/rekognition/latest/dg/API_Landmark.html

//rectrangle for face (BoundingBox)

ctx.beginPath();
ctx.lineWidth = '2';
ctx.strokeStyle = 'green';
ctx.rect(
item.BoundingBox.Left * 200,
item.BoundingBox.Top * 200,
item.BoundingBox.Width * 200,
item.BoundingBox.Height * 200);
ctx.stroke();

//line eyes
ctx.beginPath();
ctx.lineWidth = '2';
ctx.strokeStyle = 'red';
ctx.moveTo(item.Landmarks[0].X * 200, item.Landmarks[0].Y * 200);
ctx.lineTo(item.Landmarks[1].X * 200, item.Landmarks[1].Y * 200);
ctx.stroke();

//line mouth
ctx.beginPath();
ctx.lineWidth = '2';
ctx.strokeStyle = 'blue';
ctx.moveTo(item.Landmarks[3].X * 200, item.Landmarks[3].Y * 200);
ctx.lineTo(item.Landmarks[4].X * 200, item.Landmarks[4].Y * 200);
ctx.stroke();

//nose to center eyes
xeyescenter = (item.Landmarks[0].X * 200) + (item.Landmarks[1].X * 200 - item.Landmarks[0].X * 200) / 2;
yeyescenter = (item.Landmarks[0].Y * 200) + (item.Landmarks[1].Y * 200 - item.Landmarks[0].Y * 200) / 2;
ctx.beginPath();
ctx.lineWidth = '2';
ctx.strokeStyle = 'yellow';
ctx.moveTo(xeyescenter, yeyescenter);
ctx.lineTo(item.Landmarks[2].X * 200, item.Landmarks[2].Y * 200);
ctx.stroke();

/*
0- eyeLeft
1- eyeRight
2- nose
3- mouthLeft
4- mouthRight
5- leftEyeBrowLeft
6- leftEyeBrowRight
7- leftEyeBrowUp
8- rightEyeBrowLeft
9- rightEyeBrowRight
10- rightEyeBrowUp
11- leftEyeLeft XXX
12- leftEyeRight
13- leftEyeUp
14- leftEyeDown
15- rightEyeLeft
16- rightEyeRight XXX
17- rightEyeUp
18- rightEyeDown
19- noseLeft
20- noseRight
21- mouthUp
22- mouthDown
23- leftPupil
24- rightPupil
*/