ASP.NET实现上传图片并生成缩略图的方法

protected void bt_upload_Click(object sender, EventArgs e)
{
 //检查上传文件的格式是否有效 
 if (this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)
 {
 Response.Write("上传图片格式无效！");
 return;
 }
 //生成原图 
 Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength];
 System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream;
 System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);
 int oWidth = oImage.Width; //原图宽度 
 int oHeight = oImage.Height; //原图高度 
 int tWidth = 100; //设置缩略图初始宽度 
 int tHeight = 100; //设置缩略图初始高度 
 //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)));
 }
 //生成缩略原图 
 Bitmap tImage = new Bitmap(tWidth, tHeight);
 Graphics g = Graphics.FromImage(tImage);
 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量插值法 
 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置高质量,低速度呈现平滑程度 
 g.Clear(Color.Transparent); //清空画布并以透明背景色填充 
 g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel);
 string oFullName = Server.MapPath(".") + "/image/" + "o" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存原图的物理路径 
 string tFullName = Server.MapPath(".") + "/image/" + "t" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存缩略图的物理路径 
 try
 {
 //以JPG格式保存图片 
 oImage.Save(oFullName, System.Drawing.Imaging.ImageFormat.Jpeg);
 tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg);
 }
 catch (Exception ex)
 {
 throw ex;
 }
 finally
 {
 //释放资源 
 oImage.Dispose();
 g.Dispose();
 tImage.Dispose();
 }
 }
}

#region 上传图片 并生成缩略图
/// <summary>
/// 上传图片生成缩略图
/// </summary>
/// <param name="originalImagePath">图片源路径</param>
/// <param name="thumbnailPath">缩略图路径(物理路径)</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <param name="mode">生成缩略图的方式</param>
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode) {
 //从路径中获取源图片的文件
 System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
 int towidth = width;
 int toheight = height;
 int x = 0;
 int y = 0;
 //获取图片的宽度
 int ow = image.Width;
 //获取图片的高度
 int oh = image.Height;
 //生成缩略图的方式
 switch (mode) { 
 case "HW":
 break;
 case "W"://指定宽度 高按比例
 toheight = originalImage.Height * width / originalImage.Width;
 break;
 case "H"://指定图片的高度 宽按比例
 towidth = originalImage.Width * height / originalImage.Height;
 break;
 case "Cut"://如果为裁减模式 则不变形 
 if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
 {
 oh = originalImage.Height;
 //缩略图片的宽度
 ow = originalImage.Height * towidth / toheight;
 y = 0;
 x = (originalImage.Width - ow) / 2;
 }
 else {
 ow = originalImage.Width;
 //缩略图片的高度
 oh = originalImage.Width * toheight / towidth;
 x = 0;
 y(originalImage.Height - oh) / 2;
 }
 break;
 default: break;
 }
 //新建一个bmp图片
 Bitmap bitmap = new Bitmap(towidth, toheight);
 //新建一个画布 以BitMap 宽 高作为画布的大小
 Graphics g = Graphics.FromImage(bitmap);
 //设置高质量插值法
 g.InterpolationMode = InterpolationMode.High;
 //以高质量 低速度 呈现
 g.SmoothingMode = SmoothingMode.HighQuality;
 //清空画布 以白色背景色填充 
 g.Clear(Color.Transparent);
 //在指定位置并且按指定大小绘制原图片的指定部分
 g.DrawImage(originalImage,new Rectangle(towidth,toheight),new Rectangle(x,y,ow,oh),GraphicsUnit.Pixel);
 try
 {
 //以jpg格式保存缩略图
 bitmap.Save(thumbnailPath,System.Drawing.Imaging.ImageFormat.Jpeg);
 }
 catch (Exception ex)
 {
 throw ex;
 }
 finally {
 //释放资源
 originalImage.Dispose();
 bitmap.Dispose();
 g.Dispose();
 }
}
#endregion