package ppt;

import com.spire.presentation.*;
import com.spire.presentation.drawing.BackgroundType;
import com.spire.presentation.drawing.FillFormatType;
import com.spire.presentation.drawing.IImageData;
import com.spire.presentation.drawing.PictureFillType;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;

public class WatermarkDemo {

    public void watermark(String filePath, String watermarkType, String text, String imageFile, String resultFilePath) throws Exception {
        Presentation presentation = new Presentation();
        presentation.loadFromFile(filePath);

        switch (watermarkType){
            case "TEXT":
                addTextWatermark(presentation,text);
                break;
            case "IMAGE":
                File file = new File(imageFile);
                BufferedImage bufferedImage = ImageIO.read(file);
                addImageWatermark(presentation,bufferedImage);
                break;
        }
        presentation.saveToFile(resultFilePath,FileFormat.PPTX_2013);

    }

    private void addTextWatermark(Presentation presentation, String text) throws Exception {
        int width= 400;
        int height= 300;
        Rectangle2D.Double rect = new Rectangle2D.Double((presentation.getSlideSize().getSize().getWidth() - width) / 2,
                (presentation.getSlideSize().getSize().getHeight() - height) / 2, width, height);
        for (int i = 0; i< presentation.getSlides().getCount();i++){
            IAutoShape shape = presentation.getSlides().get(i).getShapes().appendShape(ShapeType.RECTANGLE,rect);
            shape.getFill().setFillType(FillFormatType.NONE);
            shape.getShapeStyle().getLineColor().setColor(Color.white);
            shape.setRotation(-45);
            shape.getLocking().setSelectionProtection(true);
            shape.getLine().setFillType(FillFormatType.NONE);
            shape.getTextFrame().setText(text);
            PortionEx textRange = shape.getTextFrame().getTextRange();
            TextFont font = new TextFont("Arial Rounded MT Bold");
            textRange.setLatinFont(font);
            textRange.getFill().setFillType(FillFormatType.SOLID);
            textRange.getFill().getSolidColor().setColor(Color.RED);
            textRange.setFontHeight(22);
        }
    }

    private void addImageWatermark(Presentation presentation, BufferedImage bufferedImage) throws DocumentEditException {
        IImageData image = presentation.getImages().append(bufferedImage);
        for (int i = 0; i< presentation.getSlides().getCount();i++) {
            ISlide slide = presentation.getSlides().get(i);
            slide.getSlideBackground().setType(BackgroundType.CUSTOM);
            slide.getSlideBackground().getFill().setFillType(FillFormatType.PICTURE);
            slide.getSlideBackground().getFill().getPictureFill().setFillType(PictureFillType.STRETCH);
            slide.getSlideBackground().getFill().getPictureFill().getPicture().setEmbedImage(image);
        }
    }
}

using Spire.Presentation;
using Spire.Presentation.Drawing;
using System.Drawing;
using System.Windows.Forms;

namespace DemoOnlineCode
{
    class AddWatermark
    {

        public void AddTextOrImageWatermarkDemo(string filePath,string format,string text, string imagePath,  string resultFileName)
        {
            Presentation presentation = new Presentation();
            presentation.LoadFromFile(filePath);
            switch (format)
            {
                case "TEXT":                   
                    AddTextWatermark(presentation,text,resultFileName);
                    break;
                case "IMAGE":
                    AddImageWatermark(presentation,imagePath,resultFileName);
                    break;
            }
        }


        private static void AddTextWatermark(Presentation presentation, string text, string resultFileName)
        {
            Form frm = new Form();
            Graphics gc = frm.CreateGraphics();
            SizeF size = gc.MeasureString(text, new Font("Lucida Sans Unicode", 50));

            //Define a rectangle range
            RectangleF rect = new RectangleF((presentation.SlideSize.Size.Width - size.Width) / 2, (presentation.SlideSize.Size.Height - size.Height) / 2, size.Width, size.Height);

            foreach (ISlide slide in presentation.Slides)
            {
                IAutoShape shape =slide.Shapes.AppendShape(ShapeType.Rectangle, rect);
                //Set the style of the shape
                shape.Fill.FillType = FillFormatType.None;
                shape.ShapeStyle.LineColor.Color = Color.White;
                shape.Rotation = -45;
                shape.Locking.SelectionProtection = true;
                shape.Line.FillType = FillFormatType.None;

                //Add text to the shape
                shape.TextFrame.Text = text;
                TextRange textRange = shape.TextFrame.TextRange;
                //Set the style of the text range
                textRange.Fill.FillType = FillFormatType.Solid;
                textRange.Fill.SolidColor.Color = Color.FromArgb(120, Color.HotPink);
                textRange.FontHeight = 50;            
            }          
            presentation.SaveToFile(resultFileName + ".pptx", FileFormat.Pptx2013);
        }

        private static void AddImageWatermark(Presentation presentation, string imageFile, string resultFileName)
        {
            IImageData image = presentation.Images.Append(Image.FromFile(imageFile));
            foreach (ISlide slide in presentation.Slides)
            {
                slide.SlideBackground.Type = BackgroundType.Custom;
                slide.SlideBackground.Fill.FillType = FillFormatType.Picture;
                slide.SlideBackground.Fill.PictureFill.FillType = PictureFillType.Stretch;
                slide.SlideBackground.Fill.PictureFill.Picture.EmbedImage = image;
            }               
            presentation.SaveToFile(resultFileName + ".pptx", FileFormat.Pptx2013);
        }
    }
}