上传图片并生成缩略图

using System;
using System.Configuration;
using System.Data;
using System.Drawing.Imaging;
using System.Drawing;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using TipDa;

//http://dcdc723.iteye.com
//by dcdc723 指尖
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlHelper sqlhelper = new SqlHelper();
        //   FileUpload1.Attributes.Add("onchange", "return show()"); 

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string name = FileUpload1.FileName;
        string size = FileUpload1.PostedFile.ContentLength.ToString();//文件大小.
        string type = FileUpload1.PostedFile.ContentType;//文件类型.
        string type2 = name.Substring(name.LastIndexOf(".") + 1);//LastIndexOf()最后一个索引位置匹配.Substring()里面的+1是重载.
        //  name = DateTime.Now.Year.ToString()+DateTime.Now.Month.ToString()+DateTime.Now.Day+DateTime.Now.Hour+DateTime.Now.Minute+DateTime.Now.Millisecond+"." + type2;
        Random rd = new Random();
        string sj = (rd.Next() + 10).ToString();
        name = DateTime.Now.ToString("yyyyMMddHHmmss") + sj + "." + type2;       
        string ipath = Server.MapPath("~/js") + "\\" + name;//取得根目录下面的路径.
        if (type2 == "jpg" || type2 == "gif" || type2 == "bmp" || type2 == "png" || type2 == "jpeg")
        {
            Response.Write(ipath);
           // Response.End();
            FileUpload1.SaveAs(ipath);//保存方法,参数是一个地址字符串.
            Label1.Text = "~/js/" + name;
            string picbig = "11";
            bool flag=false;
            FixPic2(ipath, ref picbig,ref flag);
            if (flag)
            {
             Response.Write("<font color=red>"+picbig+"</font>"); //大图名字 
            Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('上传成功！');</script>"); 
            }
           

        }
        else
        {
            Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('文件类型不正确！');</script>");

        }
    }
    protected void FileUpload1_Disposed(object sender, EventArgs e)
    {
        Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('改变');</script>");
    }




    private string FixPic2(string pic,ref string picbig,ref bool flag)
    {
        if (!System.IO.File.Exists(pic))
            return null;

        System.Drawing.Image image = System.Drawing.Image.FromFile(pic);
        if (image != null)
        {
            if (image.Width > 220 || image.Height > 220)
            {
                System.Drawing.Bitmap final_image = null;
                System.Drawing.Graphics graphic = null;
                try
                {
                    string pic1 = pic.Insert((pic.Length - 4),"_big");
                    picbig = pic1;
                    System.IO.File.Copy(pic, pic1, true);
                    int width = image.Width;
                    int height = image.Height;
                    int target_width = 220;
                    int target_height = 220;
                    int new_width, new_height;
                    float target_ratio = (float)target_width / (float)target_height;
                    float image_ratio = (float)width / (float)height;
                    if (target_ratio > image_ratio)
                    {
                        new_height = target_height;
                        new_width = (int)Math.Floor(image_ratio * (float)target_height);
                    }
                    else
                    {
                        new_height = (int)Math.Floor((float)target_width / image_ratio);
                        new_width = target_width;
                    }

                    new_width = new_width > target_width ? target_width : new_width;
                    new_height = new_height > target_height ? target_height : new_height;
                    final_image = new System.Drawing.Bitmap(target_width, target_height);
                    graphic = System.Drawing.Graphics.FromImage(final_image);
                    graphic.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.White), new System.Drawing.Rectangle(0, 0, target_width, target_height));
                    int paste_x = (target_width - new_width) / 2;
                    int paste_y = (target_height - new_height) / 2;
                    graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; /* new way */
                    //graphic.DrawImage(thumbnail_image, paste_x, paste_y, new_width, new_height);
                    graphic.DrawImage(image, paste_x, paste_y, new_width, new_height);
                    image.Dispose();
                    //string newFileName = System.IO.Path.GetDirectoryName(Server.MapPath(pic)) + "/" + System.IO.Path.GetFileNameWithoutExtension(pic) + "_s" + System.IO.Path.GetExtension(pic);
                    Response.Write(pic);
                    final_image.Save(pic, System.Drawing.Imaging.ImageFormat.Jpeg);
                    flag = true;
                  //  Response.Write("Fix OK--:" + pic + "");
                    Response.Flush();
                    //return System.IO.Path.GetDirectoryName(pic).Replace("\\", "/") + "/" + System.IO.Path.GetFileNameWithoutExtension(pic) + "_s" + System.IO.Path.GetExtension(pic);
                }
                catch (Exception ex)
                {
                    Response.Write(ex.ToString());
                }
                finally
                {
                    if (final_image != null) final_image.Dispose();
                    if (graphic != null) graphic.Dispose();
                    if (image != null) image.Dispose();
                }
            }
        }
        return null;
    }










}