private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
{
if (e.Delta < 0)
{
Console.WriteLine("mouse wheel zoom out");
SP.AxisZoom(1.5, 1.5);
GraphRender();
}
else if (e.Delta > 0)
{
Console.WriteLine("mouse wheel zoom in");
SP.AxisZoom(.5, .5);
GraphRender();
}
}