简单的上传图片并生成缩略图

页面：

<form id="form1" runat="server">
    <div>
        <asp:FileUpload ID="FileUpload1" runat="server" />
        <asp:Button ID="Button1" runat="server" Text="UP" OnClick="Button1_Click" />
    </div>
</form>

后台：　　

　　　　　protected void Button1_Click(object sender, EventArgs e)
        {
            UpImageFile(FileUpload1);
        }

        protected void UpImageFile(FileUpload fileLoad)
        {
            if (fileLoad.HasFile)
            {
                string fileType = fileLoad.PostedFile.ContentType;
                if (fileType == "image/bmp" || fileType == "image/pjpeg" || fileType == "image/gif" || fileType == "image/png")
                {
                    string loadPath = fileLoad.PostedFile.FileName;    //等待上传文件的本地路径
                    System.Drawing.Image img = System.Drawing.Image.FromFile(loadPath);
                    if (img.Height > 100 || img.Width > 100)
                    {
                        FileInfo info = new FileInfo(loadPath);
                        string fName = info.Name;   //获取原文件名
                        string fileName = DateTime.Now.ToString("yyMMddhhmmss") + fName;    //在文件名中加入时间
                        string imgPath = Server.MapPath("/UpFile/OrImages/") + fileName;    //原文件路径
                        string thPath = Server.MapPath("/UpFile/ThImages/") + fileName;     //缩略图路径
                        fileLoad.SaveAs(imgPath);   //保存原图片
                        MakeThumnail(imgPath, thPath);  //生成缩略图
                    }
                    else
                    {
                        //图片尺寸太小
                    }
                }
                else
                {
                    //文件格式不对
                }

            }
        }

        protected void MakeThumnail(string orPath, string thPath)
        {
            System.Drawing.Image img = System.Drawing.Image.FromFile(orPath);
            int width = 100;    //设置缩略图的宽为100
            int height = img.Height * width / img.Width;    //缩略图的高按比例缩小
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(width, height); //创建一个空位图
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);  //创建画板
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;  //设定为高质量插值
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;   //指定高质量低速度呈现
            g.Clear(Color.Transparent);
            g.DrawImage(img, new Rectangle(0, 0, width, height));
            try
            {
                bitmap.Save(thPath, System.Drawing.Imaging.ImageFormat.Jpeg);   //以JPG格式保存图片
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                img.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }