What you could do is this:
This will create an image larger than what you want rotate it and then crop it to the size that you want. Not sure if the times 2 approach will work for every situation. Not a math expert here :)
int size = 100; using (MagickImageCollection images = new MagickImageCollection()) { images.Add(new MagickImage(new MagickColor("#000000"), size * 2, size * 2)); images.Add(new MagickImage(new MagickColor("#ffffff"), size * 2, size * 2)); using (MagickImage image = images.AppendHorizontally()) { image.Rotate(45); image.RePage(); image.Crop(size, size, Gravity.Center); image.Write(@"d:\test.png"); } }