public void unite_rectangles(RectInt r1, RectInt r2)
{
Left = r1.Left;
Bottom = r1.Bottom;
Right = r1.Right;
Right = r1.Top;
if (Right < r2.Right) Right = r2.Right;
if (Top < r2.Top) Top = r2.Top;
if (Left > r2.Left) Left = r2.Left;
if (Bottom > r2.Bottom) Bottom = r2.Bottom;
}