ASP.NET(C#)生成缩略图

必须先引用命名空间:

  using System.IO;

 

if (FileUpload1.PostedFile.ContentType.ToLower().IndexOf("image") < 0)
        ...{
            FunctionUtility.JavaScriptHelper.Alert("上传图片格式不正确！");
            return;
        }

        //生成原图
        Byte[] oFileByte = new Byte[FileUpload1.PostedFile.ContentLength];
        Stream oStream = FileUpload1.PostedFile.InputStream;
        System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

        //原图宽度和高度
        int oWidth = oImage.Width;
        int oHeight = oImage.Height;

        //设置缩略图的初始宽度和高度
        int tWidth = 200;
        int tHeight = 200;

        //按比例计算出缩略图的宽度和高度
        if (oWidth >= oHeight)
        ...{
            tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));
        }
        else
        ...{
            tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));
        }

        //生成缩略图
        Bitmap tImage = new Bitmap(tWidth, tHeight);
        Graphics g = Graphics.FromImage(tImage);

        //指定高质量插值法
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
        //指定高质量低速度呈现
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        //清空画布并以透明背景色填充
        g.Clear(Color.Transparent);

        g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel);

        //设置文件名称
        string setFileName = FunctionUtility.FileHelper.GetDateTimeFileName()+".jpg";
        //保存原图的物理路径
        string oFullName = Server.MapPath("/DesignImages/Images/YT/" + setFileName);
        //保存缩略图物理路径
        string tFullName = Server.MapPath("/DesignImages/Images/SLT/" + setFileName);

        //以JPG格式保存图片并释放占用的资源
        try
        ...{
            oImage.Save(oFullName, System.Drawing.Imaging.ImageFormat.Jpeg);
            tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

            Image1.Visible = true;
            Image2.Visible = true;
            Image1.ImageUrl = "/DesignImages/Images/YT/" + setFileName;
            Image2.ImageUrl = "/DesignImages/Images/SLT/" + setFileName;

            FunctionUtility.JavaScriptHelper.Alert("缩略图生成成功！");
        }
       catch (Exception oe)
        ...{
            throw oe;
        }
        finally
        ...{
            oImage.Dispose();
            g.Dispose();
            tImage.Dispose();
        }