Plot Points along a line

[rickjnash]

Hi

I am trying to plot some points along a line for graphical app I am building in C#.

I have the start Point and end Point, I then draw the line. Then also want put some marks along the line. A function like this would be usefull:

Point[] PointsAlongLine(Point start, Point end, int spacing)
{
?
}

Thanks

[dannystommen]

I think this is the result

      private Point[] PointsAlongLine(Point start, Point end, int spacing) {
         int xDifference = end.X - start.X;
         int yDifference = end.Y - start.Y;
         int absoluteXdifference = Math.Abs(start.X - end.X);
         int absoluteYdifference = Math.Abs(start.Y - end.Y);

         int lineLength = (int)Math.Sqrt((Math.Pow(absoluteXdifference, 2) + Math.Pow(absoluteYdifference, 2))); //pythagoras
         int steps = lineLength / spacing;
         int xStep = xDifference / steps;
         int yStep = yDifference / steps;

         Point[] result = new Point[steps];

         for (int i = 0; i < steps; i++) {
            int x = start.X + (xStep * i);
            int y = start.Y + (yStep * i);
            result[i] = new Point(x, y);
         }

         return result;         
      }

[toraj58]

as complementary to danny for drawing the line and marking a lable in the middle of the line (as an example) you can use the function proposed by danny like this:

        protected override void OnPaint(PaintEventArgs pe)
        {
            Graphics gc = pe.Graphics;
            Pen RedPen = new Pen(Color.Red, 3);

            Point p1 = new Point(100, 100);
            Point p2 = new Point(300, 300);
            Point[] p = PointsAlongLine(p1, p2, 2); // function proposed by danny

            int pXmiddle = (p[0].X + p[p.Length - 1].X) / 2; // X axis of the point in the middle of line
            int pYmiddle = (p[0].Y + p[p.Length - 1].Y) / 2; // Y axis of the point in the middle of line

            Point middalePoint = new Point(pXmiddle, pYmiddle);

            Label lbl1 = new Label();
            lbl1.Location = middalePoint;
            lbl1.Text = "Middle of the line";

            gc.DrawLines(RedPen, p);

            this.Controls.Add(lbl1);
        }

[rickjnash]

Cheers guys I also managed to do this another way after going to www.mathisfunforum.com!!!

static public void EquationOfALine(Point start, Point end, ref double X, ref double Y)
{
Y = (end.Y - start.Y);
X = (end.X - start.X);
}

static public Point[] PointsAlongALine(Point start, Point end, int numberOfPoints)
{
Point[] points = new Point[numberOfPoints];

//Work out the equaton of the line and the add factor
double X = 0, Y = 0;
EquationOfALine(start, end, ref X, ref Y);
Y = Y / numberOfPoints;
X = X / numberOfPoints;

Point lastPoint = start;
for (int loop = 0; loop < points.Length; loop++)
{
points[loop] = new Point(lastPoint.X + (int)X, lastPoint.Y + (int)Y);
lastPoint = points[loop];
}
return points;

}

I think I can use the above code to help with another problem. I need to find a point X Pixels from the start or end of the line.

[toraj58]

in order to find the middle of the line you can do this:

            int pXmiddle = (p[0].X + p[p.Length - 1].X) / 2; // X axis of the point in the middle of line
            int pYmiddle = (p[0].Y + p[p.Length - 1].Y) / 2; // Y axis of the point in the middle of line

to find other the logic is similar that (e.g. quarter, one-eighth...)
and base in pixel it as alread in this array Point[] p that you can access each element base on index of the array.