从数据库加载后获取黑色图像

Question

经过一段时间的尝试并在这里寻找一些答案后，我无法从 MySQL 加载图像。

基本上，用户从OpenFileDialog 中选择一张图片，然后将其加载到PictureBox 中（这工作正常）。
然后用户单击一个按钮，该按钮将通过将图片转换为byte[] 将图片保存在数据库中。
最后，当我尝试在另一个PictureBox 中加载图片时，全黑了。

添加图片到db时：

public void PictureToDB(Image img)
{
    MemoryStream tmpStream = new MemoryStream();
    img.Save(tmpStream, ImageFormat.Png);
    tmpStream.Seek(0, SeekOrigin.Begin);
    byte[] imgBytes = new byte[5000];
    tmpStream.Read(imgBytes, 0, 5000);

    string query = "Update TABLE Set IMG = @imgBytes";
    MySqlParameter param = new MySqlParameter("@img", imgBytes);

    //Skipping connection to db and all... it works
}

从数据库中获取图片：

public void DBToPicture()
{
    string query = "Select IMG From TABLE Where ...";
    //Skipping Command lines ...
    MySqlDataReader reader = command.ExecuteReader();
    DataTable myDT.Load(reader);

    Byte[] data = new Byte[0];
    data = (Byte[])(myDT.Rows[0]["PHOTOLOISANT"]);
    MemoryStream mem = new MemoryStream(data);
    MyPictureBox.Image = Image.FromStream(mem);
}

更多信息：

• the type in MySQL is varbinary(8000) and contains this "89504e470d0a1a0a0000000d4948445200000280000001e00802000000bab34bb3000000017352474200aece1ce90000000467414d41002e2e2e" after the update
• 图片在第一个PictureBox加载时会转换为位图。

Answer 1

用于存储：

conn = new MySqlConnection("server=" + hostname + ";uid=" + username + ";pwd=" + password + ";database=databaseimage;Charset=latin1;");
            conn.Open();
            FileStream fs;
            Byte[] bindata;
            MySqlParameter picpara;
            cmd = new MySqlCommand("INSERT INTO mypic (pic) VALUES(?pic)", conn);
            picpara = cmd.Parameters.Add("?pic", MySqlDbType.MediumBlob);
            cmd.Prepare();

//txtPicPath is the path of the image, e.g. C:\MyPic.png

            fs = new FileStream(txtPicPath.Text, FileMode.Open, FileAccess.Read);
            bindata = new byte[Convert.ToInt32(fs.Length)];
            fs.Read(bindata, 0, Convert.ToInt32(fs.Length));
            fs.Close();

            picpara.Value = bindata;
            cmd.ExecuteNonQuery();

要检索它：

if (conn == null) // Just to make sure that the connection was not severed
        {


                conn = new MySqlConnection("server=" + hostname + ";uid=" + username + ";pwd=" + password + ";database=databaseimage;Charset=latin1;");
                conn.Open();

        }
        MemoryStream ms = new MemoryStream();
        FileStream fs;
        Byte[] bindata;

        cmd = new MySqlCommand("SELECT pic FROM mypic WHERE id=3", conn);
        bindata = (byte[])(cmd.ExecuteScalar());



        ms.Write(bindata, 0, bindata.Length);
        pb2.Image = new Bitmap(ms);

        fs = new FileStream(name, FileMode.Create, FileAccess.Write);
        ms.WriteTo(fs);

我将使用这些步骤从 MySql 存储和检索图像。

此致，

蒂亚古·拉金德兰

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