在图片上加水印或写字

使用一般处理程序在已有图片上加水印或者写字

public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            //原图
            System.Drawing.Bitmap bitmap = new Bitmap(context.Server.MapPath("Uploads/201307269946.jpg"));
            //水印图
            System.Drawing.Bitmap bitmap1 = new Bitmap(context.Server.MapPath("Uploads/201307269390.png"));

            Graphics g = Graphics.FromImage(bitmap);

            //Drawing String
            //g.DrawString("www.cnblogs.com/g1mist", new Font("黑体", 30), Brushes.Red, new PointF(10, 60));

            //Drawing Images
            //将水印图画在原图的(10,60)位置上
            g.DrawImage(bitmap1, new Point(10, 60));

            bitmap.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);

        }

　　但是，一个一般处理程序一次在一张图片上加水印，如果需要在每一个对图片的请求中都对图片加上水印，那就要使用全局处理程序，新建一个类"WaterMarkHelper",并且实现IHttpHandler接口

public class WaterMarkHelper : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            //原始请求路径
            string rawurl = context.Request.RawUrl;
            //取到物理路径
            string path = context.Server.MapPath(rawurl);
            //取到水印的路径
            string logoPath = context.Server.MapPath("201307269390.png");

            //原图
            using (Image img = Image.FromFile(path))
            {
                //水印图
                using (Image logoImage = Image.FromFile(logoPath))
                {
                    //原图为画板
                    using (Graphics g = Graphics.FromImage(img))
                    {
                        //在原图上画上水印
                        g.DrawImage(logoImage, 10, 60, logoImage.Width, logoImage.Height);

                        //保存图片
                        img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                    }
                }
            }
        }

        public bool IsReusable
        {
            get { return false; }
        }
    }

　　接着在Web.config中进行配置：

　　.net 4.5:

　　

<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
  </system.web>
  <system.webServer>
    <handlers>
      <add name="water" verb="*" path="Uploads/*.jpg" type="FileUpload.WaterMarkHelper"/>
    </handlers>
  </system.webServer>
</configuration>

　　.net 4.0

　　

<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
    <httpHandlers>
      <add verb="*" path="Uploads/*.jpg" type="FileUpload.WaterMarkHelper"/>
    </httpHandlers>
  </system.web>
</configuration>

　　type: "命名空间.类名,程序集名称",如果没有命名空间就只写类名。和网站在同一个程序集就不用写程序及名称