How to add image watermark in PowerPoint document in C#

Spire.Presentation offer developers an easy way to add the watermarks to the presentation slides. There are two kinds of watermarks in PowerPoint documents: text watermark and image watermark. We'll learn how to add image watermark in PowerPoint document via Spire.Presentation.

The goal of the article is to make an image as a background img watermark as following screenshot.

How to add image watermark in PowerPoint document in C#

Here comes to the steps of how to add image watermarks in C#:

Step 1: Create a presentation document and load the document from the file

Presentation ppt = new Presentation();
ppt.LoadFromFile(fileName);

Step 2: Get the image you want to add as image watermark.

IImageData image = ppt.Images.Append(Image.FromFile("Header.png"));

Step 3: Set the properties of SlideBackground, and then fill the image as watermark.

ppt.Slides[0].SlideBackground.Type = Spire.Presentation.Drawing.BackgroundType.Custom;
ppt.Slides[0].SlideBackground.Fill.FillType = FillFormatType.Picture;
ppt.Slides[0].SlideBackground.Fill.PictureFill.FillType=PictureFillType.Stretch;
ppt.Slides[0].SlideBackground.Fill.PictureFill.Picture.EmbedImage = image;

step4: Save the document to a new file.

ppt.SaveToFile(resultFileName, Spire.Presentation.FileFormat.PPT);

Full codes:

Presentation ppt = new Presentation();
ppt.LoadFromFile(fileName);
IImageData image = ppt.Images.Append(Image.FromFile("Header.png"));
ppt.Slides[0].SlideBackground.Type = Spire.Presentation.Drawing.BackgroundType.Custom;
ppt.Slides[0].SlideBackground.Fill.FillType = FillFormatType.Picture;
ppt.Slides[0].SlideBackground.Fill.PictureFill.FillType=PictureFillType.Stretch;
ppt.Slides[0].SlideBackground.Fill.PictureFill.Picture.EmbedImage = image;

if (fileExtensions == ".ppt")
 {
   ppt.SaveToFile(resultFileName, Spire.Presentation.FileFormat.PPT);
 }
   else
 {
   ppt.SaveToFile(resultFileName, Spire.Presentation.FileFormat.Pptx2007);
 }

Viewer(resultFileName);