ASP.NET：使用ashx进行预览时图像质量下降

Question

我的网页允许用户上传图像，并将图像保存到SQL Server，并将图像显示给用户。以下代码是我保存图像的方式：

FileUpload img = (FileUpload)fileUploadLocationPic;
Byte[] imgByte = null;
string strFileExtension = Path.GetExtension(img.PostedFile.FileName.ToString());

// Create a FILE
HttpPostedFile File = fileUploadLocationPic.PostedFile;

// Create byte array
imgByte = new Byte[File.ContentLength];

// force control to load data
File.InputStream.Read(imgByte, 0, File.ContentLength);

strQuery = "INSERT INTO [Table](Image) VALUES(@LocImage)";
SqlParameter ParamLocImage = new SqlParameter();
ParamLocImage.ParameterName = "@LocImage";
ParamLocImage.Value = imgByte;
cmd.Parameters.Add(ParamLocImage);

以下是我使用ashx从数据库中检索的方法：

public Stream ShowEmpImage(string PLID){
            string connectionString = WebConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;

            //string conn = ConfigurationManager.ConnectionStrings["EmployeeConnString"].ConnectionString;
            SqlConnection connection = new SqlConnection(connectionString);
            string sql = "SELECT [Image] FROM [Table] WHERE [ID] = @PLID";

            SqlCommand cmd = new SqlCommand(sql, connection);
            cmd.CommandType = CommandType.Text;
            cmd.Parameters.AddWithValue("@PLID", PLID);
            connection.Open();
            object img = cmd.ExecuteScalar();
            try
            {
                return new MemoryStream((byte[])img);
            }
            catch
            {
                return null;
            }
            finally
            {
                connection.Close();
            }
}

public void ProcessRequest(HttpContext context){
            string PLID = "";
            PLID = (context.Request.QueryString["PLID"]);

            context.Response.ContentType = "image/jpg";
            Stream strm;
            strm = ShowEmpImage(PLID);
            int count = 2048;
            byte[] buffer = new byte[count];    
            int byteSeq = 0;
            try
            {
                byteSeq = strm.Read(buffer, 0, count);
            }
            catch
            {                   
            }   
            while (byteSeq > 0)
            {
                context.Response.OutputStream.Write(buffer, 0, byteSeq);
                byteSeq = strm.Read(buffer, 0, count);
            }
}

最后，我使用

<asp:Image ID="imageChargingLocation" runat="server" /> imageChargingLocation.ImageUrl = "~/Editor/ShowImage.ashx?PLID=" + strPLID;

检索图像。 但是我的图像质量下降了。 我该怎么办？ （图像是jpg。尝试png时同样的问题。）