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How do I apply an image watermark to a PDF using Quick PDF Library?

Yes, Quick PDF Library can add an image watermark to a PDF programmatically. I've included some Delphi sample code below that demonstrates how to do this.

This sample code will apply a watermark to every page in the selected PDF. The location of the watermark can easily be changed by updating the co-ordinates for the DrawImage function.

procedure TForm2.btnImageWatermarkClick(Sender: TObject);
var
  PDFOriginal: Integer;
  ImagePath: AnsiString;
  WatermarkID: Integer;
  PageHeight: Double;
  PageWidth: Double;
  OutputPath: AnsiString;
  I: Integer;
begin
  QP := TQuickPDF0718.Create;
  try
    // Insert trial or paid license key here
    UnlockResult := QP.UnlockKey('..Insert License Key Here...');
    if UnlockResult = 1 then
    begin
    // Load the PDF that you want to watermark
    if dlgOpen.Execute then
      begin
         QP.LoadFromFile(dlgOpen.FileName);
         PDFOriginal := QP.SelectedDocument();
      end;
      // Load the image that you want to use as the watermark
      if dlgOpen.Execute then
      begin
         ImagePath := dlgOpen.FileName;
      end;
      // This is setup for use with PNG images.
      // Check out AddImageFromFile function in the
      // reference guide for info on other image types.
      WatermarkID := QP.AddImageFromFile(ImagePath, 0);

      // Loop through each page in the document
      // and apply the watermark.
      for I := 1 to QP.PageCount() - 1 do
      begin
        QP.SelectPage(I);
        PageHeight := QP.PageHeight();
        PageWidth := QP.PageWidth();
        QP.SelectImage(WatermarkID);
        QP.SetOrigin(1);
        QP.DrawImage(100, 100, QP.ImageWidth(), QP.ImageHeight());
      end;
      // Save the watermarked PDF to disk
    if dlgSave.Execute then
      begin
        OutputPath := dlgSave.FileName;
      end;
      QP.SaveToFile(OutputPath);
    end;
  finally
    QP.Free;
  end;
end;