使用HttpHandler为图片添加水印

需求：

1、为所有的大图添加水印

2、不要直接在图片上生成水印，要保持图片的原汁原味

3、要求可配置，配置的选项包括是否启用水印，水印图片可以更换，水印的位置可以更换

解决方案：

    在我们的图片管理系统中，用户上传的图片都通过一个二级域名进行管理，如 images.photocms.com

所以就只需在这个应用中，拦截所有的图片请求交由asp.net处理，在asp.net程序中处理原图和水印图片，

将结果输出给用户即可。

    具体步骤如下：

    1、配置IIS，将jpg后缀名的请求用aspnet_isapi.dll来接收处理。

    2、配置Web.config ，添加.jpg处理程序对应的具体asp.net类

       <add verb="*" path="*.jpg" type="PhotoCms.Common.WaterMark,PhotoCms.Common" />

具体技术实现：

    其中具体的 HttpHandler 程序

 

  public class WaterMark : IHttpHandler

    {
        public void ProcessRequest(HttpContext context)
        {
            HttpResponse Response = context.Response;
            HttpRequest Request = context.Request;

            Response.ContentType = "image/jpeg";
            string filePath = Request.FilePath;
            string physicalPath = context.Server.MapPath(filePath);


            if (!File.Exists(physicalPath))
                return;



            string waterImagePath = context.Server.MapPath("/watermark.png");
            IList<string> ruleList=new List<string>();
            string isOpen=string.Empty;
            int padding = 10;

            watermarkConfig objWaterConfig = watermarkConfig.GetInstance();
            if (objWaterConfig != null)
            {
                isOpen=objWaterConfig.isOpen;
                waterImagePath = context.Server.MapPath(objWaterConfig.filePath);
                ruleList = objWaterConfig.rules;
                padding = objWaterConfig.padding;
            }

            
            bool doWaterMark=false;
            foreach(string _rule in ruleList)
            {
                if(filePath.Contains(_rule))
                {
                    doWaterMark=true;
                    continue;
                }
            }

            if(isOpen.Equals("1") && doWaterMark)                       
            {
                physicalPath = context.Server.MapPath(filePath);                
                ImageHelper obj = new ImageHelper(physicalPath);
                obj.InsertImage(waterImagePath, Common.WathermarkPosition.BottomRight,padding);
                obj.GetImage().Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                obj.Dispose();
            }
            else
            {
                physicalPath = context.Server.MapPath(filePath);
                byte[] buffer = new Byte[10000];
                int length;
                long dataToRead;
                System.IO.Stream iStream = null;

                iStream = new System.IO.FileStream(physicalPath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
                dataToRead = iStream.Length;

                Response.Buffer = false;
                while (dataToRead > 0)
                {
                    if (Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);
                        Response.OutputStream.Write(buffer, 0, length);
                        Response.Flush();

                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        dataToRead = -1;
                    }
                }
                iStream.Close();

            }

        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        
    }

    public class watermarkConfig
    {
        public string isOpen = string.Empty;
        public string filePath = string.Empty;
        public int padding = 0;
        public IList<string> rules=new List<string>();

        private static watermarkConfig instance;
        private watermarkConfig()
        {
            loadConfigFile();            
        }

        public static watermarkConfig GetInstance()
        {
            if (instance == null)
            {
                instance = new watermarkConfig();            
            }
            return instance;            
        }

        private void loadConfigFile()
        {
            string configFile = HttpContext.Current.Request.ApplicationPath + "/config/photo/photo.config";
            XmlDocument xml = new XmlDocument();
            xml.Load(HttpContext.Current.Server.MapPath(configFile));

            XmlNode waterroot = xml.SelectSingleNode("picture/watermark");
            this.isOpen = waterroot.Attributes["isOpen"].Value;
            this.filePath = waterroot.Attributes["filePath"].Value;
            this.padding = Convert.ToInt32(waterroot.Attributes["padding"].Value);
            foreach(XmlNode rule in waterroot.ChildNodes)
            {
                if (rule.NodeType != XmlNodeType.Comment)
                {
                    if (rule.Name.ToLower().Equals("rule"))
                    { 
                        rules.Add(rule.Attributes["urlfrom"].Value);                    
                    }
                }
            
            }
        }
    }

 

 

/config/photo/photo.config 的内容

 

<!--水印设置，isOpen 1开启水印 其他值关闭，filePath 水印图片的物理路径， rule 包含哪些字符串的图片需要加水印-->

  <watermark isOpen="1" filePath="~/watermark.png" padding="100">

    <rule urlfrom="/photo/e0"></rule>

    <rule urlfrom="/photo/f0"></rule>

    <rule urlfrom="/photo/a0"></rule>

  </watermark>