HOWTO: C# example to rotate image and annotations.

private void RotateImageAndAnnotations( int angle, AnnContainer container, RasterImageViewer viewer )
{
   // round the angle 
   angle %= 360;
   if ( angle == 0 )
      return; // nothing to do 
   // when we rotate an image, this is what happens: 
   // 1. the image is rotated around its center (width/2, height/2) 
   // 2. the image is translated so that its top,left position is at 0,0 
   // to calculate this translation, we: 
   // 1. find the 4 end points of the container 
   // 2. rotate these points 
   // 3. find the minimum/maximum "out of range" point 
   // 4. calculate the translation (amount to bring this "out of range"point back into view) 
   PointF[] pts =
   {
      new PointF( 0, 0 ),
      new PointF( viewer.Image.ImageWidth, 0 ),
      new PointF( viewer.Image.ImageWidth, viewer.Image.ImageHeight ),
      new PointF( 0, viewer.Image.ImageHeight )
   };
   PointF origin = new PointF( viewer.Image.ImageWidth / 2, viewer.Image.ImageHeight / 2 );
   using ( var m = new Matrix() )
   {
      m.RotateAt( angle, origin );
      m.TransformPoints( pts );
   }
   float xMin = pts[0].X;
   float yMin = pts[0].Y;
   for ( int i = 1; i < pts.Length; i++ )
   {
      if ( pts[i].X < xMin )
         xMin = pts[i].X;
      if ( pts[i].Y < yMin )
         yMin = pts[i].Y;
   }
   float xTranslate = -xMin;
   float yTranslate = -yMin;
   // now, rotate the image 
   new RotateCommand( angle * 100, RotateCommandFlags.Resize, RasterColor.FromGdiPlusColor( Color.White ) )
   .Run( viewer.Image );
   // rotate and translate the annotations 
   foreach ( AnnObject obj in container.Objects )
   {
      obj.Rotate( angle, new AnnPoint( origin ) );
      if ( xTranslate != 0 || yTranslate != 0 )
         obj.Translate( xTranslate, yTranslate );
   }
   // re-set the container bounds 
   container.Bounds = new AnnRectangle( 0, 0, viewer.Image.ImageWidth, viewer.Image.ImageHeight );
}