เพิ่มลายน้ำข้อความไปยัง PPTX ผ่าน C#

// create a Presentation from scratch
using (var presentation = new Aspose.Slides.Presentation())
{
    // get the Master Slide to add watermark on all slides
    var master = presentation.Masters[0];
    // add a new shape using IShapeColection.AddAutoShape
    var shape = master.Shapes.AddAutoShape(Aspose.Slides.ShapeType.Triangle, 0, 0, 0, 0);
    // set watermark text
    shape.AddTextFrame("CONFIDENTIAL");
    // save presentation in PPTX format
    presentation.Save("output.pptx", Aspose.Slides.Export.SaveFormat.Pptx);
}