/// <summary>
/// Calculates an axis aligned rectangle which fully contains an arbitrarily transformed axis aligned rectangle.
/// </summary>
/// <param name="rectangle">Original bounding rectangle.</param>
/// <param name="transform">World transform of the rectangle.</param>
/// <returns>A new rectangle which contains the trasnformed rectangle.</returns>
public static void CalculateBoundingRectangle(ref RectangleF rectangle, ref Matrix transform, out RectangleF boundingRect)
{
// Get all four corners in local space
Vector2 leftTop;
leftTop.X = rectangle.Left;
leftTop.Y = rectangle.Top;
Vector2 rightTop;
rightTop.X = rectangle.Right;
rightTop.Y = rectangle.Top;
Vector2 leftBottom;
leftBottom.X = rectangle.Left;
leftBottom.Y = rectangle.Bottom;
Vector2 rightBottom;
rightBottom.X = rectangle.Right;
rightBottom.Y = rectangle.Bottom;
// Transform all four corners into work space
Vector2Helper.Transform(ref leftTop, ref transform, out leftTop);
Vector2Helper.Transform(ref rightTop, ref transform, out rightTop);
Vector2Helper.Transform(ref leftBottom, ref transform, out leftBottom);
Vector2Helper.Transform(ref rightBottom, ref transform, out rightBottom);
// Find the minimum and maximum extents of the rectangle in world space
Vector2 min = Vector2.Min(Vector2.Min(leftTop, rightTop), Vector2.Min(leftBottom, rightBottom));
Vector2 max = Vector2.Max(Vector2.Max(leftTop, rightTop), Vector2.Max(leftBottom, rightBottom));
// Return that as a rectangle
boundingRect = new RectangleF();
boundingRect.X = min.X;
boundingRect.Y = min.Y;
boundingRect.Width = (max.X - min.X);
boundingRect.Height = (max.Y - min.Y);
}