学步园

新建一个Handler.ashx  的文件直接copy下面的代码：

public class AddWaterPic : IHttpHandler
{
    public AddWaterPic()
    {
        //
        //TODO: 在此处添加构造函数逻辑
        //
    }

    private const string LOGO = "~/Logo.png"; //水印图片
    private readonly float ALPHA = 1.0f; //透明度

    /// <summary>
    /// 指示IHttpHandler 实例是否可再次使用
    /// </summary>
    public bool IsReusable
    {
        get { return true; }
    }

    public void ProcessRequest(HttpContext context)
    {     //获取请求的物理图片路径
        if (context.Request.QueryString["u"] != null)
        {
            string imgSrc = context.Request.QueryString["u"];
            string imagePath = context.Server.MapPath("~/Upload/BigPic/" + imgSrc);

            System.Drawing.Image image = null;
            if (File.Exists(imagePath))
            {
                image = new Bitmap(imagePath);
                System.Drawing.Image images = Drawing(image, context.Server.MapPath(LOGO));
                context.Response.ContentType = "image/jpeg";//输出图片的类型
                images.Save(context.Response.OutputStream, ImageFormat.Jpeg);//将添加水印的图片输入到当前流中
                image.Dispose();
            }
            context.Response.End();
        }
    }

    //给图片添加水印
    private System.Drawing.Image Drawing(System.Drawing.Image image, string logo)
    {
        Graphics g = Graphics.FromImage(image); //获得Graphics 对象
        System.Drawing.Image watermark = System.Drawing.Image.FromFile(logo);//将水印图片放入watermark 对象
        //关于透明度(使用颜色矩阵)
        float[][] nArray ={ new float[] {1, 0, 0, 0, 0},
             new float[] {0, 1, 0, 0, 0},
             new float[] {0, 0, 1, 0, 0},
             new float[] {0, 0, 0,ALPHA , 0},
             new float[] {0, 0, 0, 0, 1}};
        ColorMatrix colormatrix = new ColorMatrix(nArray);
        ImageAttributes attributes = new ImageAttributes();
        attributes.SetColorMatrix(colormatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
        g.DrawImage(watermark, new Rectangle(image.Width - watermark.Width - 20, image.Height - watermark.Height - 15,
watermark.Width, watermark.Height), 0, 0, watermark.Width, watermark.Height, GraphicsUnit.Pixel, attributes);//在图片指定坐标处放入一个矩形图片内容为水印图片
        g.Dispose();
        watermark.Dispose();
        return image;
    }
}

2.在web.config中记得配置 <add verb="*" type="Handler的名" path="自己命名"/>     <remove verb="*" path="*.asmx"/>例如：

<add verb="*" type="AddWaterPic" path="WaterImgs"/>
      <remove verb="*" path="*.asmx"/>

 在调用的时候：this.imgUrl.ImageUrl = "WaterImgs?u=" + pic.PImgpath;

这种加水印的方法好在不修改原来的图片～很好用的～