Hi, You can perform the Transformation on your Points(By just adding or subtracting (100, 100) to each points). GDI+ uses (0,0) is the Mid point. But it provides Matrix class to Transform the Coordinate System.
Example to Transform the Coordinate System
private void Form1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
Rectangle rect = new Rectangle (0,0,100,100);
Matrix matrix = new Matrix();
g.DrawEllipse(Pens.Blue, rect);
matrix.Translate(100, 100);
g.Transform = matrix;
g.DrawEllipse(Pens.Green, rect);
}
Here first Circle will be drawn Blue color and (0,0) as the starting point
Second circle will use the Transformation and (100,100) as the starting Point
I think this may helpful to you
Unsolved 
