对文档添加水印可以有效声明和保护文档，是保护重要文件的方式之一。在PPT文档中同样也可以设置水印，包括文本水印和图片水印，本文将讲述如何通过Spire.Presentation for .NET来对PPT添加水印，下载安装Free Spire.Presentationfor .NET后，添加引用dll文件，参考下面的操作步骤，完成水印添加。

1.添加文本水印

步骤一：初始化Presentation类实例，并加载文档

Presentation ppt = newPresentation();
ppt.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.pptx", FileFormat.Pptx2010);

步骤二：初始化一个Font类实例，并实例化字体格式

Font stringFont = new Font("Arial", 90);
Size size= TextRenderer.MeasureText("内部资料", stringFont);

步骤三：绘制一个shape并指定大小、填充颜色、边框颜色和旋转角度

RectangleF rect = new RectangleF((ppt.SlideSize.Size.Width - size.Width) / 2, (ppt.SlideSize.Size.Height - size.Height) / 2, size.Width, size.Height);
IAutoShape shape= ppt.Slides[0].Shapes.AppendShape(Spire.Presentation.ShapeType.Rectangle, rect);
shape.Fill.FillType=FillFormatType.None;
shape.ShapeStyle.LineColor.Color=Color.White;
shape.Rotation= -45;

步骤四：设定形状属性为保护属性

shape.Locking.SelectionProtection = true;
shape.Line.FillType= FillFormatType.None;

步骤五：设置文本大小、颜色

shape.TextFrame.Text = "内部资料";
TextRange textRange=shape.TextFrame.TextRange;
textRange.Fill.FillType=Spire.Presentation.Drawing.FillFormatType.Solid;
textRange.Fill.SolidColor.Color= Color.FromArgb(120, Color.Gray);
textRange.FontHeight= 45;

步骤六：保存文档

ppt.SaveToFile("TextWatermark.pptx", FileFormat.Pptx2010);

完成以上代码步骤后，调试运行项目程序，生成文件（可在该项目文件中bin>Debug中查看），如下图所示：

全部代码：

usingSystem;usingSystem.Text;usingSpire.Presentation;usingSystem.Drawing;usingSpire.Presentation.Drawing;usingSystem.Windows.Forms;namespaceInsertWatermark_PPT
{classProgram{static void Main(string[] args){//初始化一个Presentation类实例并加载文档Presentation ppt = newPresentation();ppt.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.pptx", FileFormat.Pptx2010);//初始化一个Font类字体实例并实例化字体格式Font stringFont = new Font("Arial", 90);Size size= TextRenderer.MeasureText("内部资料", stringFont);//绘制一个Shape并指定大小、填充颜色、边框颜色和旋转度RectangleF rect = new RectangleF((ppt.SlideSize.Size.Width - size.Width) / 2, (ppt.SlideSize.Size.Height - size.Height) / 2, size.Width, size.Height);IAutoShape shape= ppt.Slides[0].Shapes.AppendShape(Spire.Presentation.ShapeType.Rectangle, rect);shape.Fill.FillType=FillFormatType.None;shape.ShapeStyle.LineColor.Color=Color.White;shape.Rotation= -45;//设定形状属性为保护属性shape.Locking.SelectionProtection = true;shape.Line.FillType=FillFormatType.None;//设置文本大小、颜色shape.TextFrame.Text = "内部资料";TextRange textRange=shape.TextFrame.TextRange;textRange.Fill.FillType=Spire.Presentation.Drawing.FillFormatType.Solid;textRange.Fill.SolidColor.Color= Color.FromArgb(150, Color.LightBlue);textRange.FontHeight= 90;//保存文档ppt.SaveToFile("TextWatermark.pptx", FileFormat.Pptx2010);}}

2.添加图片水印

步骤一：初始化一个Presentation类实例并加载文档

Presentation ppt = newPresentation();
ppt.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.pptx", FileFormat.Pptx2010);

步骤二: 为第一张幻灯片设置背景图片类型和样式

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;

步骤三：加载图片并为第一张幻灯片设置水印

Image img = Image.FromFile(@"C:\Users\Administrator\Desktop\images\1.jpg");
IImageData image=ppt.Images.Append(img);
ppt.Slides[0].SlideBackground.Fill.PictureFill.Picture.EmbedImage = image;

步骤四：保存文档

 ppt.SaveToFile("ImageWatermark1.pptx", FileFormat.Pptx2010);

全部代码：

usingSystem;usingSystem.Drawing;usingSpire.Presentation;usingSpire.Presentation.Drawing;namespaceImageWatermark_PPT
{classProgram{static void Main(string[] args){//初始化一个Presentation类实例并加载文档Presentation ppt = newPresentation();ppt.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.pptx", FileFormat.Pptx2010);//为第一张幻灯片设置背景图片类型和样式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;//加载图片并为第一张幻灯片设置水印效果Image img = Image.FromFile(@"C:\Users\Administrator\Desktop\images\1.jpg");IImageData image=ppt.Images.Append(img);ppt.Slides[0].SlideBackground.Fill.PictureFill.Picture.EmbedImage =image;//保存文档ppt.SaveToFile("ImageWatermark1.pptx", FileFormat.Pptx2010);}}
}

以上是对PPT添加水印的代码操作，希望该方法能提供帮助，感谢阅读！