private static Image DrawText(String text, System.Drawing.Font font, Color textColor, Color backColor, double height, double width){//创建一个指定宽度和高度的位图图像Image img = new Bitmap((int)width, (int)height);Graphics drawing = Graphics.FromImage(img);//获取文本大小SizeF textSize = drawing.MeasureString(text, font);//旋转图片drawing.TranslateTransform(((int)width - textSize.Width) / 2, ((int)height - textSize.Height) / 2);drawing.RotateTransform(-45);drawing.TranslateTransform(-((int)width - textSize.Width) / 2, -((int)height - textSize.Height) / 2);//绘制背景
            drawing.Clear(backColor);//创建文本刷Brush textBrush = new SolidBrush(textColor);drawing.DrawString(text, font, textBrush, ((int)width - textSize.Width) / 2, ((int)height - textSize.Height) / 2);drawing.Save();return img;}private void button1_Click(object sender, EventArgs e){//初始化一个新工作簿并加载要添加水印的文件Workbook workbook = new Workbook();workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.xlsx");//在页眉插入图片Font font = new System.Drawing.Font("arial", 40);String watermark = "测试水印";foreach (Worksheet sheet in workbook.Worksheets){//调用DrawText()方法新建图片System.Drawing.Image imgWtrmrk = DrawText(watermark, font, System.Drawing.Color.LightCoral, System.Drawing.Color.White, sheet.PageSetup.PageHeight, sheet.PageSetup.PageWidth);//将页眉图片设置为左对齐sheet.PageSetup.LeftHeaderImage = imgWtrmrk;sheet.PageSetup.LeftHeader = "&G";//水印只会在此种模式下显现sheet.ViewMode = ViewMode.Layout;}workbook.SaveToFile("测试水印.xlsx", ExcelVersion.Version2010);System.Diagnostics.Process.Start("测试水印.xlsx");}