با سلام
مي شود لطفا در مورد قسمت هاي bold شده توضيحي دهيد.

Point [] po = new Point[4];
int x1, y1, x2, y2;
int x01, y01, x02, y02;
x01 = Convert.ToInt32(textBox1.Text );
y01 = Convert.ToInt32(textBox2 .Text );
x02 = Convert.ToInt32(textBox3.Text);
y02 = Convert.ToInt32(textBox4.Text);

Graphics g = pictureBox1.CreateGraphics();
Pen n_pen = new Pen(Color.Blue,2);
x1 = 125 + Convert.ToInt32(textBox1.Text);
y1 = 125 - Convert.ToInt32(textBox2.Text);
x2 = 125 + Convert.ToInt32(textBox3.Text);
y2 = 125 - Convert.ToInt32(textBox4.Text);

po[0].X = x1; po[0].Y = y1;
po[1].X = x2; po[1].Y = y1;
po[2].X = x1; po[2].Y = y2;
po[3].X = x2; po[3].Y = y2;

g.DrawLine(n_pen, po[0], po[1]);
g.DrawLine(n_pen, po[0], po[2]);
g.DrawLine(n_pen, po[1], po[3]);
g.DrawLine(n_pen, po[2], po[3]);