private void UpdateMedium()
{
MyPoint different = EndPoint - StartPoint;
Point1.Set(StartPoint.X + 3 * different.X / 8, StartPoint.Y + 1 * different.Y / 8);
Point2.Set(StartPoint.X + 5 * different.X / 8, StartPoint.Y + 7 * different.Y / 8);
}
private void StartSelect(MyPoint point)
{
Visible = true;
Point1.Set(point);
}