Transparent Picture DrawImage

Hi all.

When creating a PDF I am using the function "DrawImage". But I use a picture with a transparent background. However, after applying the function instead of the picture remains black area. Just in the size of the picture.
Is there an option to save the image with a transparent background?

Best regards

Hello 

This is part of my code:

MemoryStream arrowMS = new MemoryStream();
arrowBmp.Save(arrowMS, ImageFormat.Png);
arrowBmp.Save("arrow " + (ctln) + ".png");
res = qp.AddImageFromVariant(arrowMS.GetBuffer(), 0);
res = qp.SelectImage(res);
res = qp.DrawImage(0, 0, this.Width, this.Height);

I'll try to use Bitmap.MakeTransparent() metod. But same result.
Method GetPixel(1,1) was returns full transparent - (0,0,0,0).

It mean that picture is transparent.