使用 ASP.NET 从 SQL Server 检索时图像质量下降

Question

I'm using ASP.NET to build a webpage which allow user to upload images. I use the following code to convert image to image byte:

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);

Then I save imgByte into SQL Server. But when I retrieve image byte from SQL Server, I can see that the image quality has decreased. Can anyone tell me how to solve this problem? Thanks in advance.

EDIT: The way I show image is using ashx handler:

        SqlConnection connection = new SqlConnection(connectionString);
        string sql = "SELECT [ChargingBoxLocationImage] FROM [Parking Lot] 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);
        }

And then in aspx , use

imageChargingLocation.ImageUrl = "~/Editor/ShowImage.ashx?PLID=" + strPLID;

It will be obvious to see the difference if you zoom in.

Answer 1

The code you have posted is fine since you are copying the bytes directly from the image. What does your code look like that reads the data and sends it to the client?

As long as you don't load the bytes into a Bitmap and then call Bitmap.Save , your code will not decrease the image quality.