Apply Watermark to Presentation Slides in C# using .NET API

AddImageWatermarkToPresentation.cs

// Add image watermark to presentation slides in C# using .NET API
using (Watermarker watermarker = new Watermarker("presentation.pptx"))
{
    // Set watermark image, coordinates and formatting
    ImageWatermark imageWatermark = new ImageWatermark("watermark-image.png");
    imageWatermark.Opacity = .7;
    imageWatermark.X = 80;
    imageWatermark.Y = 120;
    
    // Apply Watermark to only second slide of the presentation
    PresentationWatermarkSlideOptions ImageWatermarkOptions = new PresentationWatermarkSlideOptions();
    ImageWatermarkOptions.SlideIndex = 1;

    // Add watermark to presentation and save.
    watermarker.Add(imageWatermark, ImageWatermarkOptions);
    watermarker.Save("image-watermarked-presentation.pptx");
}

AddTextWatermarkToPresentation.cs

// Add text watermark to presentation slides in C# using .NET API
using (Watermarker watermarker = new Watermarker("presentation.pptx"))
{
    // Set watermark text, coordinates and formatting
    TextWatermark watermark = new TextWatermark("Watermark", new Font("Arial", 36))
    {
        RotateAngle = -45,
        X = 100,
        Y = 100,
        Height = 400,
        Width = 400,
        Opacity = .2,
        ForegroundColor = Color.DarkBlue,
        HorizontalAlignment = HorizontalAlignment.Center,
        VerticalAlignment = VerticalAlignment.Center
    };
    // Apply Watermark to only first slide of the presentation
    PresentationWatermarkSlideOptions textWatermarkOptions = new PresentationWatermarkSlideOptions();
    textWatermarkOptions.SlideIndex = 0;
    
    // Add watermark to presentation and save.
    watermarker.Add(watermark, textWatermarkOptions);
    watermarker.Save("text-watermarked-presentation.pptx");
}