/// <summary>
/// Draws rectangle annotation.
/// </summary>
/// <param name="image">Image.</param>
/// <param name="rect">User specified area to annotate.</param>
/// <param name="text">Label.</param>
/// <param name="annotationWidth">Width of annotation rectangle.</param>
/// <param name="color">Color for rectangle. Label area is filled. Default color is yellow-green.</param>
/// <param name="textColor">Label color. Default color is black.</param>
/// <param name="font">Font to use. Default is "Arial" of size 10, style: Bold.</param>
/// <param name="thickness">Rectangle thickness.</param>
public static void DrawAnnotation(this Image <Bgr, byte> image, Rectangle rect, string text,
int annotationWidth = 100, Bgr color = default(Bgr), Bgr textColor = default(Bgr), Font font = null,
int thickness = 1)
{
color = color.Equals(default(Bgr)) ? Color.YellowGreen.ToBgr() : color;
textColor = textColor.Equals(default(Bgr)) ? Color.Black.ToBgr() : color;
font = font ?? new Font("Arial", 8, System.Drawing.FontStyle.Bold);
var nLines = text.Where(x => x.Equals('\n')).Count() + 1;
var annotationHeight = (int)(3 + (font.SizeInPoints + 3) * nLines + 3);
var xOffset = (annotationWidth - rect.Width) / 2;
var annotationRect = new Rectangle(rect.X - xOffset, rect.Y - annotationHeight, annotationWidth, annotationHeight);
image.Draw(annotationRect, color, thickness);
image.Draw(rect, color, thickness);
image.Draw(annotationRect, color, -1, 80);
image.Draw(text, font, annotationRect, textColor);
}