public enum JPEGColorMode : System.Enum, System.IComparable, System.IConvertible, System.IFormattable, System.ISpanFormattable  

{
  //Export a map frame to JPG.
  string filePath = @"Path and file name for the output export file";
  //Create JPEG format with appropriate settings
  //BMP, EMF, EPS, GIF, PDF, PNG, SVG, TGA, and TFF formats are also available for export
  JPEGFormat JPG = new JPEGFormat()
  {
    HasWorldFile = true,
    Resolution = 300,
    OutputFileName = filePath,
    ColorMode = JPEGColorMode.TwentyFourBitTrueColor,
    Height = 800,
    Width = 1200
  };

  //Reference the map frame
  MapFrame mf = layout.FindElement("MyMapFrame") as MapFrame;

  //Export on the worker thread
  //Note: Must be on QueuesTask.Run
  //Check to see if the path is valid and export
  if (JPG.ValidateOutputFilePath())
  {
    mf.Export(JPG);  //Export the map frame to JPG
  }
}