图片的修改(上传图片时，做的缩小或放大操作）

        string sFileName = Path.GetFileNameWithoutExtension(this.FileUpload1.FileName);
        string sExtension = Path.GetExtension(FileUpload1.FileName);
        double size = FileUpload1.PostedFile.ContentLength / 1024;
        if (size < 60)
        {
            string fi = Server.MapPath(@"img/") + sFileName + sExtension;
            if (sExtension == ".gif" || sExtension == ".jpg" || sExtension == ".bmp" || sExtension == ".png")
            {
                System.Drawing.Image image = System.Drawing.Image.FromStream(this.FileUpload1.PostedFile.InputStream);
                int width = image.Width;
                int height = image.Height;
                int max = 40;
                try
                {
                    System.Drawing.Image newPic;
                    if (width > height)
                    {
                        newPic = new System.Drawing.Bitmap(image, max, height * max / width);
                    }
                    else
                    {
                        newPic = new System.Drawing.Bitmap(image, width * max / height, max);
                    }
                    newPic.Save(fi, System.Drawing.Imaging.ImageFormat.Jpeg);
                    img1.Src = @"img\" + sFileName + sExtension;
                }
                catch (Exception ex)
                {

                }
            }
        }