Position a label on a face

Hi all,

I try to put a label on a face.

I use that 2 tutorials to find a solution (sorry I can't put link, I don't know why):
mr-azure-304
mr-azure-310

both tutorials are on Microsoft website

I use this function to find the face in the quad:

Code (CSharp):

1. /// <summary>
2.     /// This method hosts a series of calculations to determine the position
3.     /// of the Bounding Box on the quad created in the real world
4.     /// by using the Bounding Box received back alongside the Best Prediction
5.     /// </summary>
6.     public Vector3 CalculateBoundingBoxPosition(Bounds b, BoundingBox boundingBox)
7.     {
8.         Debug.Log($"BB: left {boundingBox.left}, top {boundingBox.top}, width {boundingBox.width}, height {boundingBox.height}");
9.  
10.         double centerFromLeft = boundingBox.left + (boundingBox.width / 2);
11.         double centerFromTop = boundingBox.top + (boundingBox.height / 2);
12.         Debug.Log($"BB CenterFromLeft {centerFromLeft}, CenterFromTop {centerFromTop}");
13.  
14.         double quadWidth = b.size.normalized.x;
15.         double quadHeight = b.size.normalized.y;
16.         Debug.Log($"Quad Width {b.size.normalized.x}, Quad Height {b.size.normalized.y}");
17.  
18.         double normalisedPos_X = (quadWidth * centerFromLeft) - (quadWidth/2);
19.         double normalisedPos_Y = (quadHeight * centerFromTop) - (quadHeight/2);
20.  
21.         return new Vector3((float)normalisedPos_X, (float)normalisedPos_Y, 0);
22.     }

My problem is when I receive the bouding box I have pixel and my quand is another unit. when I give that vector to my label, my label is far of the face.

Do you have an idea how can I do that? I know the size of the picture, the size of the quad but I think my quad can be bigger then my picture.

Thanks guys!