将图片等比例缩小不影响图片的分辨率

#region 生成缩略图    ///     /// 生成缩略图    ///     /// 传入图片的路径    private void SaveImage(string filePath)    {        string fileName = Path.GetExtension(File1.PostedFile.FileName).ToLower();        string _filename = DateTime.Now.ToString("yyMMddHHmm");        System.Drawing.Image image = null, aNewImage = null;        //下面是生成缩略图         int newwidth = 0, newheight = 0;        image = System.Drawing.Image.FromFile(filePath);        System.Drawing.Image.GetThumbnailImageAbort callb = new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);        //取高和宽           int phWidth = image.Width;        int phHeight = image.Height;        //设置缩略的宽度和高度        if (phWidth > 110)        {            //指定宽度            newwidth = 110;            //根据宽度算出高度            newheight = phHeight * newwidth / phWidth;        }        aNewImage = image.GetThumbnailImage(newwidth, newheight, callb, new System.IntPtr());        //将缩略图重新命名并保存        aNewImage.Save(Server.MapPath("~/upload/") + "Avaster_" + DateTime.Now.ToString("yyMMddHHmm") + fileName);        image.Dispose();    }    #endregion