Here is C# example that demonstrates how to generate barcode with transparent background: 
public static System.Drawing.Bitmap GenerateBarcodeWithTransparentBackground(Vintasoft.Barcode.BarcodeType type, string value)
{
    Vintasoft.Barcode.BarcodeWriter writer = new Vintasoft.Barcode.BarcodeWriter();
    writer.Settings.Barcode = type;
    writer.Settings.Value = value;
    writer.Settings.PixelFormat = Vintasoft.Barcode.BarcodeImagePixelFormat.Bgra32;
    writer.Settings.BackColor = System.Drawing.Color.Transparent;
    return writer.GetBarcodeAsBitmap();
}