C#图片加水印(Generate Watermark Picture)

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

namespace CSFramework.BLL
{
   public class WatermarkImage
   {
      /// <summary>
      /// 在图片上添加水印文字
      /// </summary>
      /// <param name="sourcePicture">源图片文件</param>
      /// <param name="waterWords">需要添加到图片上的文字</param>
      /// <param name="webName">网站名称</param>
      /// <param name="alpha">透明度</param>
      /// <returns></returns>
      public string DrawWords(string sourcePicture, string waterWords, string webName, float alpha)
      {
         // 判断参数是否有效
         if (sourcePicture == string.Empty || waterWords == string.Empty || alpha == 0.0)
         {
            return sourcePicture;
         }
         
         string PicturePath = Path.GetDirectoryName(sourcePicture) "\\";
         string fileExtension = System.IO.Path.GetExtension(sourcePicture).ToLower();
         
         // 判断文件是否存在,以及文件名是否正确
         if (System.IO.File.Exists(sourcePicture) == false || (
         fileExtension != ".gif" &&&
         fileExtension != ".jpg" &
         fileExtension != ".png"))
         {
            return sourcePicture;
         }
         
         //创建一个图片对象用来装载要被添加水印的图片
         Image imgPhoto = Image.FromFile(sourcePicture);
         
         //获取图片的宽和高
         int phWidth = imgPhoto.Width;
         int phHeight = imgPhoto.Height;
         
         //建立一个bitmap，和我们需要加水印的图片一样大小
         Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);
         
         //SetResolution：设置此 Bitmap 的分辨率
         //这里直接将我们需要添加水印的图片的分辨率赋给了bitmap
         bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
         
         //Graphics：封装一个 GDI 绘图图面。
         Graphics grPhoto = Graphics.FromImage(bmPhoto);
         grPhoto.SmoothingMode = SmoothingMode.AntiAlias;//设置图形的品质
         
         //将我们要添加水印的图片按照原始大小描绘（复制）到图形中
         grPhoto.DrawImage(
         imgPhoto, // 要添加水印的图片
         new Rectangle(0, 0, phWidth, phHeight), // 根据要添加的水印图片的宽和高
         0, // X方向从0点开始描绘
         0, // Y方向
         phWidth, // X方向描绘长度
         phHeight, // Y方向描绘长度
         GraphicsUnit.Pixel); // 描绘的单位，这里用的是像素
         
         int m_alpha = Convert.ToInt32(256 * alpha);
         SolidBrush alphaBrush = new SolidBrush(Color.FromArgb(m_alpha, 175, 175, 175)); //设置画笔透明度及颜色
         
         DrawMainWords(imgPhoto, grPhoto, alphaBrush, waterWords);
         DrawWebTitleWords(imgPhoto, grPhoto, alphaBrush, webName);
         
         imgPhoto.Dispose();
         imgPhoto = bmPhoto;//重新设置引用
         grPhoto.Dispose();
         
         // 目标图片名称及全路径
         string targetImage = Path.GetDirectoryName(sourcePicture) "\\" DateTime.Now.ToString("yyyyMMddhhmmss") ".png";
         
         //将grPhoto保存
         imgPhoto.Save(targetImage, ImageFormat.Png);
         imgPhoto.Dispose();
         
         File.Delete(sourcePicture);//删除旧的图片
         File.Move(targetImage, sourcePicture);//文件改名
         
         return targetImage.Replace(PicturePath, "");
      }
      
      private void DrawWebTitleWords(Image imgPhoto, Graphics g, SolidBrush alphaBrush, string waterWords)
      {
         Font font = new Font("黑体", 12, FontStyle.Bold);
         
         SolidBrush brush = new SolidBrush(Color.FromArgb(Convert.ToInt32(0.3 * 256), 175, 175, 175)); //设置画笔透明度及颜色
         
         g.DrawString(waterWords, font, brush, imgPhoto.Width / 2 - 30, 40); //绘制文字
      }
      
      private void DrawMainWords(Image imgPhoto, Graphics g, SolidBrush alphaBrush, string waterWords)
      {
         //**********绘制倾斜文字**************
         Font font = new Font("Verdana", 26, FontStyle.Bold);
         SizeF size = g.MeasureString(waterWords, font);
         Single posX = 10;
         Single posY = Convert.ToSingle(imgPhoto.Height * 0.8); //高度位置80%处
         g.TranslateTransform(posX, posY);
         
         Matrix transform = g.Transform;
         //float shearX = -0.230F; //右倾斜文字
         float shearX = 0.50F; //左倾斜文字
         float shearY = -0.50F;
         
         transform.Shear(shearX, shearY);
         g.Transform = transform;
         
         g.DrawString(waterWords, font, alphaBrush, 0, 0); //绘制文字
      }
   }
}


// 来源:www.CSFramework.com, C/S结构框架学习网