This code is working correctly using the 8.16 release.  It creates a problem with the 8.15 release so it looks like there was a bug fix in the 8.16 release that allows this to work correctly.

8.16 is a free upgrade from 8.xx and can be downloaded from http://www.debenu.com/products/development/debenu-pdf-library/updates/

    QP.SetOrigin(1);

    QP.SetLineWidth(2);

    for (int i = 1; i <= 16; i++)

    {

        QP.SetLineColor(0, (double)i / 16, (double)i / 16);

        QP.DrawLine(i * 16, 0, i * 16, 200);

    }

    int img = QP.AddImageFromFile("test.bmp", -1);

    QP.SelectImage(img);

    QP.SetImageMask(0.9, 0.9, 0.9, 1, 1, 1); // THIS SHOULD WORK FOR YOU

    QP.DrawImage(0,0, 100, 100);

    QP.SaveToFile("out.pdf");

It seems that when using the code above - AcrobatX does some interesting things when rendering this file.  If the zoom is less than 100% then a white box is drawn under the signature. Zooming in then shows the correct background.  I beleive this is an Acrobat rendering problem.

Another option is to call QP.SetBlendMode(3); before calling DrawImage and then calling QP.SetBlendMode(0);   Currenty QuickPDF Library cannot render blend modes but we are working to add this feature.

 

//SignControl3 is a monochrome bitmap

//SignControl2 is predefined 256 color palette

 

      SignControl3->Picture->LoadFromFile(OpenPictureDialog->FileName);

      SignControl2->Width = SignControl3->Width;                      
      SignControl2->Height = SignControl3->Height;

      TRect src = Rect(0,0, SignControl3->Width, SignControl3->Height);
      TRect dest = Rect(0, 0,SignControl2->Picture->Bitmap->Width, SignControl2->Picture->Bitmap-   >Height);
      SignControl2->Picture->Bitmap->Canvas->CopyRect(dest, SignControl3->Canvas, src);
      SignControl2->Picture->SaveToFile(OpenPictureDialog->FileName);

      SignControl->Picture->LoadFromFile(OpenPictureDialog->FileName);

I was not able to get the SetPNGTransparencyColor() to work, but 

 

Thanks