Print image as transparent

Hi, I would like to print an image as transparent.

I am using the parameter opacity but, when I change it, the image does not print. This is my code:

private ZMotifGraphics _context;

public void DrawPhoto(byte[] sourcePhoto, PhotoNodeType node)


            _context.ImageFromByteArray(ref sourcePhoto);

            _context.DrawImage(ref sourcePhoto, node.PosX, node.PosY, node.Width, node.Height, 0);


The last parameter is the opacity. If I include other two parameters (transparencyColorLow and transparencyColorHigh) but they enlarge the image, they do not make it transparent.

Could you, please, tell me if it is possible set opacity when the image is going to be printed?

Thanks in advance,