Converts bitonal images to an enhanced 8-bits gray-scaled indexed color image. 

The color table has 256 entries.

public GdPictureStatus ConvertBitonalToGrayScale(
    int ImageID, 
    int SoftenValue
);

Public Function ConvertBitonalToGrayScale(
    ByVal ImageID As Integer, 
    ByVal SoftenValue As Integer
) As GdPictureStatus

A member of the GdPictureStatus enumeration.