To draw a rectangle around the face from given eye positions, get inspired by the following code snippet (written in C#) to obtain face rectangle coordinates.

public static Vector[] GetFaceRectangle(Vector leftEyeVec, Vector rightEyeVec)  {
            Vector eyeVec = leftEyeVec - rightEyeVec;
            double eyeDist = eyeVec.Length;

            double widthFace = eyeDist /  0.25d; //ICAO ratios
            double heigthFace = widthFace / 0.75d;
            Vector n = eyeVec.Unit().Normal(); //normalize

            Vector[] result = new Vector[5];  
            result[0] = new Vector(rightEyeVec.X, rightEyeVec.Y);  //find out origin of the rectangle
            result[0] -= n * (heigthFace * 0.45d);
            result[0] -= eyeVec.Unit() * ((widthFace - eyeDist) / 2.0);

            result[1] = result[0] + eyeVec.Unit() * widthFace;
            result[2] = result[1] + n * heigthFace;
            result[3] = result[0] + n * heigthFace;
            result[4] = new Vector(widthFace, heigthFace);
            return result;
}

class Vector {
        public double X, Y;
        public double Length {
            get { return Math.Sqrt(X * X + Y * Y); }
        }
        public Vector(double x, double y){
            this.X = x;  this.Y = y;
        }
        public static Vector operator +(Vector a, Vector b) {
            return new Vector(a.X + b.X, a.Y + b.Y);
        }
        public static Vector operator -(Vector a, Vector b) {
            return new Vector(a.X - b.X, a.Y - b.Y);
        }
        public static Vector operator *(Vector a, double b) {
            return new Vector(a.X * b, a.Y * b);
        }
       public static Vector operator /(Vector a, double d) {
            return new Vector(a.X / d, a.Y / d);
        }  
        public Vector Unit() {
            return this / this.Length;
        }
        public Vector Normal() {
            return new Vector(Y, -X) * -1;
        }
    }