we are converting the attached pptx file to a PDF with the following code and the resulting PDF shows black bars on top and bottom.
var presentation = Presentation.Open(fileStream);
var doc = PresentationToDPdfConverter.Convert(presentation);
var pdfStream = new MemoryStream();
On further analyzing the reported problem, we have found that the transparency is applied for gradient stops for two rectangle shapes in front of the image in the input PowerPoint document.