How to add a point in somewhere between two points of a complete polygon

Question

I have a list of points. I take first one and very next point (second point) and draw a line between first and second point.

I want to add another vertex in between existing points.

This is my method.

when user double clicks on line a point should be added there.

find all points of shape generated by polygon.

check if e.Location is in the list of points.

if exists then check that point's lowerbound and upperbound.

insert that e.Location next to lowerbound.

Re-draw the lines with updated list.

I'm calculating all points of lines. by using y = mx + c.

My problem is I'm able to get all vertical points x = a, some diagonal points and Horizontal points but not all. I need to know what is the cause and how can I fix it ?
I'm creating a bitmap overlay provided by ICImaging video grabber library.So I'm limited to pass only integer points to draw on screen.

   private void btnAddPoint_Click(object sender, EventArgs e)
    {
        //IsLineSelected = true;
        Debug.Print("Current Points in List ");
        foreach (System.Drawing.Point P in PathPoints)
        {
            Debug.Print(P.ToString());
        }
        for (int IndexI = 0; IndexI != PathPoints.Count - 1; IndexI++)
        {
            if (IndexI  == PathPoints.Count-1)
            {
                break;
            }
            else
            {
                Debug.Print("P1:" + PathPoints[IndexI].ToString() + "P2:"+ PathPoints[IndexI+1].ToString());
                ShapeDirectory.AllLinePoints(PathPoints[IndexI], PathPoints[IndexI + 1]);
            }

        }

        foreach (System.Drawing.Point P in ShapeDirectory.LinePoints)
        {
            PathPoints3.Add(P);
        }
        drawLinePoints = true;

    }        

    public static void AllLinePoints(Point p1, Point p2)
    {

        double YDiff = p2.Y - p1.Y;
        double XDiff = p2.X - p1.X;

        double SlopM = Math.Round(Math.Abs(YDiff / XDiff));

        double YinterceptB = Math.Round(Math.Abs(p1.Y - (SlopM * p1.X)));

        Debug.Print("Slop: " + SlopM.ToString() + "Y Intercept: " + YinterceptB.ToString());

        if (SlopM == 0)
        {

        }


        if (Double.IsNegativeInfinity(SlopM) || Double.IsPositiveInfinity(SlopM))
        {
            int LowerBoundX = 0;
            int LowerBoundY = 0;

            int upperBoundX;
            int upperBoundY;

            double distanceBetwwenP1andp2 = GetDistanceBetween2points(p1, p2);

            if (p1.X == p2.X )
            {
                LowerBoundX = p1.X;
                upperBoundX = p2.X;                   

            }

            if (p1.Y <= p2.Y)
            {
                LowerBoundY = p1.Y;
                upperBoundY = p2.Y;

            }
            else
            {
                LowerBoundY = p2.Y;
                upperBoundY = p1.Y;
            }

            //Vertical 

            for (int YIndex = LowerBoundY; YIndex <= upperBoundY; YIndex++)
            {

                        TempLinePoint.X = LowerBoundX;
                        TempLinePoint.Y = YIndex;

                        //Debug.Print("Current Line Points X: " + XIndex.ToString() + "Y: " + YIndex.ToString());
                        LinePoints.Add(TempLinePoint);                            
            }
        }
        else 
        {
            int LowerBoundX;
            int LowerBoundY;

            int upperBoundX;
            int upperBoundY;

            double distanceBetwwenP1andp2 = GetDistanceBetween2points(p1, p2);

            if (p1.X <= p2.X && p1.Y <= p2.Y)
            {
                LowerBoundX = p1.X;
                upperBoundX = p2.X;

                LowerBoundY = p1.Y;
                upperBoundY = p2.Y;

            }
            else
            {
                LowerBoundX = p2.X;
                upperBoundX = p1.X;

                LowerBoundY = p2.Y;
                upperBoundY = p1.Y;

            }

            //if Vertical 
            for (int YIndex = LowerBoundY; YIndex <= upperBoundY; YIndex++)
            {

                for (int XIndex = LowerBoundX; XIndex <= upperBoundX; XIndex++)
                {
                    if (YIndex == (SlopM * XIndex) + YinterceptB)
                    {
                        TempLinePoint.X = XIndex;
                        TempLinePoint.Y = YIndex;

                        //Debug.Print("Current Line Points X: " + XIndex.ToString() + "Y: " + YIndex.ToString());
                        LinePoints.Add(TempLinePoint);

                    }
                }
            }

        }

Edit

I have changed my method.

Calculate center point.

Add New MouseDoubleClicked e.Location to PathPoint List.

Find the angle of every vertex of polygon.

Sort list in ascending order.

Insert the first PointAt End of list to complete Polygon.

Code is in the answer.

Answer 1

    public static double GetAngleBetweenPoints(Point p1, Point p2)
    {           
        double xDiff = p2.X - p1.X;
        double yDiff = p1.Y - p2.Y;

        double Angle = Math.Atan2(yDiff, xDiff) * (180 / Math.PI);

        if (Angle < 0.0)
            Angle = Angle + 360.0;

        return Angle;
    }

 public static GenericList<Point> PointAddingByAngle(GenericList<Point> LinePoints2)
    {

        List<int> AnglefromCenterPointsofShapePoint = new List<int>();
        List<Point> Linepoints3 = new List<Point>(LinePoints2);
        List<Point> LinePoints = Linepoints3.Distinct().ToList();

        Point CenterPoint = new Point();
        CenterPoint.X = PolygonCenterX;
        CenterPoint.Y = PolygonCenterY;            

        for (int index = 0; index < LinePoints.Count; index++)
        {
            AnglefromCenterPointsofShapePoint.Add((int) Math.Round(GetAngleBetweenPoints(CenterPoint, LinePoints[index])));    
        }           


        AnglefromCenterPointsofShapePoint.Sort();

        int currentPointAngle = 0;

        for (int AngleListIndex = 0; AngleListIndex < AnglefromCenterPointsofShapePoint.Count; AngleListIndex++)
        {
            currentPointAngle = AnglefromCenterPointsofShapePoint[AngleListIndex];

            for (int index = 0; index < LinePoints.Count; index++)
            {
                if ((Math.Round(GetAngleBetweenPoints(CenterPoint, LinePoints[index]))) == currentPointAngle)
                {
                    SortedPoints.Add(LinePoints[index]);
                    break;
                }
            }
        }

        SortedPoints.Add(SortedPoints[0]);
        return SortedPoints;
    }


   private void pictureBox_MouseDoubleClick(object sender, MouseEventArgs e)
    {
        if (PathPoints.Count > 2)
        {
            PathPoints.Add(PathPoints[0]);
            IsPathComplete = true;
            IsPointSelected = false;
            StartingPoint = PathPoints[0];
            EndingPoint = PathPoints[PathPoints.Count - 1];
        }

        if (IsPathComplete && NewPointAdd)
        {

            System.Drawing.Point Centerpoint = new System.Drawing.Point();

            PathPoints.Add(e.Location);

            MinMaxFinder(PathPoints);

            Centerpoint.X = PolygonCenterX;
            Centerpoint.Y = PolygonCenterY;


            lblAngle.Text = Convert.ToString(Math.Round(ShapeDirectory.GetAngleBetweenPoints(Centerpoint, e.Location)));

            PathPoints3.Clear();

            PathPoints3 = ShapeDirectory.PointAddingByAngle(PathPoints);

            PathPoints.Clear();

            foreach (System.Drawing.Point p in PathPoints3)
            {
                PathPoints.Add(p);
            }

            PathPoints.Add(PathPoints3[0]);
            NewPointAddDraw = true;
        }
    }