将图像存储到数据库 blob；从数据库检索到 Picturebox

Question

您好，我之前发布了此内容并获得了一些帮助，但仍然没有有效的解决方案。感谢上次的问答，我已经确定了我的“保存到数据库”代码以及“检索到图片”代码有问题。即使我手动将图片保存在数据库中，它仍然无法检索。这是我根据网络上的 3 或 4 个示例拼凑而成的代码。理想情况下，如果有人有一些已知的良好代码并且可以指导我使用它，那将是最好的。

    Dim filename As String = txtName.Text + ".jpg"
    Dim FileSize As UInt32
    Dim ImageStream As System.IO.MemoryStream

    ImageStream = New System.IO.MemoryStream
    PbPicture.Image.Save(ImageStream, System.Drawing.Imaging.ImageFormat.Jpeg)
    ReDim rawdata(CInt(ImageStream.Length - 1))
    ImageStream.Position = 0
    ImageStream.Read(rawdata, 0, CInt(ImageStream.Length))
    FileSize = ImageStream.Length

    Dim query As String = ("insert into actors (actor_pic, filename, filesize) VALUES    (?File, ?FileName, ?FileSize)")
    cmd = New MySqlCommand(query, conn)
    cmd.Parameters.AddWithValue("?FileName", filename)
    cmd.Parameters.AddWithValue("?FileSize", FileSize)
    cmd.Parameters.AddWithValue("?File", rawData)

    cmd.ExecuteNonQuery()

    MessageBox.Show("File Inserted into database successfully!", _
    "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)

![在此处输入图像描述][1]

'*****使用以下代码检索图片框：

  Private Sub GetPicture()
    'This retrieves the pictures from a mysql DB and buffers the rawdata into a memorystream 

    Dim FileSize As UInt32
    Dim rawData() As Byte

    Dim conn As New MySqlConnection(connStr)


    conn.Open()
    conn.ChangeDatabase("psdb")


    Dim cmd As New MySqlCommand("SELECT actor_pic, filesize, filename FROM actors WHERE actor_name = ?autoid", conn)
    Cmd.Parameters.AddWithValue("?autoid", Actor1Box.Text)

    Reader = cmd.ExecuteReader
    Reader.Read()

    'data is in memory 

    FileSize = Reader.GetUInt32(Reader.GetOrdinal("filesize"))
    rawData = New Byte(FileSize) {}

    'get the bytes and filesize 

    Reader.GetBytes(Reader.GetOrdinal("actor_pic"), 0, rawData, 0, FileSize)

    Dim ad As New System.IO.MemoryStream(100000)
    ' Dim bm As New Bitmap

    ad.Write(rawData, 0, FileSize)

    Dim im As Image = Image.FromStream(ad) * "error occurs here" (see below)
    Actor1Pic.Image = im


    Reader.Close()


    conn.Close()
    conn.Dispose()

    ad.Dispose()

Answer 1

好吧，自从没有得到帮助后，我就解决了这个问题，并最终让它发挥作用。这是我的工作代码。

从 Picturebox 中保存到 MySQL (pbPicture)

    Dim filename As String = txtName.Text + ".jpg"
    Dim FileSize As UInt32

    conn.Close()

    Dim mstream As New System.IO.MemoryStream()
    PbPicture.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
    Dim arrImage() As Byte = mstream.GetBuffer()

    FileSize = mstream.Length
    Dim sqlcmd As New MySqlCommand
    Dim sql As String
    mstream.Close()

    sql = "insert into [your table]  (picture, filename, filesize) 
                               VALUES(@File, @FileName, @FileSize)"

    Try
        conn.Open()
        With sqlcmd
            .CommandText = sql
            .Connection = conn
            .Parameters.AddWithValue("@FileName", filename)
            .Parameters.AddWithValue("@FileSize", FileSize)
            .Parameters.AddWithValue("@File", arrImage)

            .ExecuteNonQuery()
        End With
    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        conn.Close()
    End Try

从 MySQL 数据库加载 返回到 Picturebox

   Dim adapter As New MySqlDataAdapter
    adapter.SelectCommand = Cmd

    data = New DataTable

    adapter = New MySqlDataAdapter("select picture from [yourtable]", conn)

注意！只能将一张图片放入图片框中，因此显然此查询只能为您返回一条记录

    commandbuild = New MySqlCommandBuilder(adapter)
    adapter.Fill(data)

    Dim lb() As Byte = data.Rows(0).Item("picture")
    Dim lstr As New System.IO.MemoryStream(lb)
    PbPicture.Image = Image.FromStream(lstr)
    PbPicture.SizeMode = PictureBoxSizeMode.StretchImage
    lstr.Close()

Answer 2

接受和赞成的答案可能有效，但它不是最理想的，而且相当浪费：

1. 如果要保存的图像在磁盘上，则没有理由使用 UI 控件和 MemoryStream 将图像放入字节数组中。
2. 该代码似乎还重用了单个全局连接对象；这些应该被创建和处理，而不是重复使用。
3. 考虑仅将文件名保存到数据库（可能经过哈希处理），并将图像保存到特殊文件夹。保存图像数据会使数据库膨胀并且转换时间更长。
4. 最后，.GetBuffer() 是完全不正确的：
   memstream 缓冲区通常包含未使用的已分配字节。对于 25k 的测试文件，ToArray() 返回 25434 字节 - 图像的正确大小 - 而 GetBuffer() 返回 44416。图像越大，空字节越多将有。

---

它使用 MySQL 提供程序对象，因为它是这样标记的，但使用的数据提供程序（MySQL、SQLServer、OleDB 等）并不重要：它们都工作相同。

如果图像源是 PictureBox，请使用 MemoryStream：

Dim picBytes As Byte()
Using ms As New MemoryStream()
    picBox1.Image.Save(ms, imgFormat)
    picBytes = ms.ToArray()        ' NOT GetBuffer!
End Using

由于图像必须来自某个地方，如果它是文件，这就是您所需要的：

picBytes = File.ReadAllBytes(filename)

一旦您将图像作为字节，保存：

Dim SQL = "INSERT INTO <YOUR TBL NAME> (picture, filename, filesize) VALUES(@Pic, @FileName, @FileSize)"

Using conn As New MySqlConnection(connstr)
    Using cmd As New MySqlCommand(SQL, conn)
        conn.Open()

        cmd.Parameters.Add("@Pic", MySqlDbType.Blob).Value = picBytes
        cmd.Parameters.Add("@FileName", MySqlDbType.String).Value = filename
        cmd.Parameters.Add("@FileSize", MySqlDbType.Int32).Value = FileSize

        cmd.ExecuteNonQuery()

    End Using
End Using            ' close and dispose of Connection and Command objects

从数据库加载图像

Dim imgData As Byte()

'... open connection, set params etc
Using rdr As MySqlDataReader = cmd.ExecuteReader

    If rdr.HasRows Then
        rdr.Read()
        imgData = TryCast(rdr.Item("Image"), Byte())
        ' in case this record has no image
        If imgData IsNot Nothing Then
             ' ToDo: dispose of any previous Image

            ' create memstream from bytes
            Using ms As New MemoryStream(imgData)
                ' create image from stream, assign to PicBox
                picBox1.Image = CType(Image.FromStream(ms), Image)

            End Using
        End If
    End If
End Using

请注意，必须处理Bitmaps和Images。如果您在用户浏览数据库时重复创建新图像，您的应用程序将会泄漏并最终崩溃。如果您经常来回转换，您可以编写一个帮助程序或扩展方法来将图像转换为字节，反之亦然。

DBConnection 和 DBCommand 对象也需要被处理。 Using 块为我们完成了这个任务。

参考资料、资源：

• 重用或处置数据库连接？示例 GetConnection helper
• 连接池
• MemoryStream.GetBuffer()
• 我们可以停止使用 AddWithValue 吗()

Answer 3

使用 MySQL 和 VB.NET 存储和检索图像的经过测试的代码

Public Class FMImage

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    If OpenFileDialog1.ShowDialog(Me) = Windows.Forms.DialogResult.OK Then
        TextBox1.Text = OpenFileDialog1.FileName

        Dim filename As String = TextBox1.Text
        Dim FileSize As UInt32

        Dim Conn As MySql.Data.MySqlClient.MySqlConnection
        Conn = New MySql.Data.MySqlClient.MySqlConnection

        Try
            If Conn.State = ConnectionState.Open Then Conn.Close()
            Conn.ConnectionString = MySQLConnectionString
            Conn.Open()

        Catch ex As Exception
            MessageBox.Show(ex.ToString, "Connect")
        End Try


        Dim mstream As System.IO.MemoryStream = ConvertImageFiletoMemoryStream(filename)
        PbPicture.Image.Save(mstream, Drawing.Imaging.ImageFormat.Jpeg)
        Dim arrImage() As Byte = ConvertImageFiletoBytes(filename)

        FileSize = mstream.Length
        Dim sqlcmd As New MySql.Data.MySqlClient.MySqlCommand
        Dim sql As String
        mstream.Close()

        'CREATE TABLE `actors` ( `actor_pic` longblob,`filesize` bigint(20) default NULL,`filename` varchar(150) default NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1;

        sql = "insert into actors (actor_pic, filesize, filename) VALUES(@File, @FileName, @FileSize)"

        Try

            With sqlcmd
                .CommandText = sql
                .Connection = Conn
                .Parameters.AddWithValue("@FileName", filename)
                .Parameters.AddWithValue("@FileSize", FileSize)
                .Parameters.AddWithValue("@File", arrImage)
                .ExecuteNonQuery()
            End With
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try


        Dim adapter As New MySql.Data.MySqlClient.MySqlDataAdapter
        adapter.SelectCommand = New MySql.Data.MySqlClient.MySqlCommand("SELECT actor_pic, filesize, filename FROM actors", Conn)

        Dim Data As New DataTable
        'adapter = New MySql.Data.MySqlClient.MySqlDataAdapter("select picture from [yourtable]", Conn)

        Dim commandbuild As New MySql.Data.MySqlClient.MySqlCommandBuilder(adapter)
        adapter.Fill(Data)
        MsgBox(Data.Rows.Count)


        Dim lb() As Byte = Data.Rows(Data.Rows.Count - 1).Item("actor_pic")
        Dim lstr As New System.IO.MemoryStream(lb)
        PbPicture.Image = Image.FromStream(lstr)
        PbPicture.SizeMode = PictureBoxSizeMode.StretchImage
        lstr.Close()

    End If
End Sub

Public Function ConvertImageFiletoBytes(ByVal ImageFilePath As String) As Byte()
    Dim _tempByte() As Byte = Nothing
    If String.IsNullOrEmpty(ImageFilePath) = True Then
        Throw New ArgumentNullException("Image File Name Cannot be Null or Empty", "ImageFilePath")
        Return Nothing
    End If
    Try
        Dim _fileInfo As New IO.FileInfo(ImageFilePath)
        Dim _NumBytes As Long = _fileInfo.Length
        Dim _FStream As New IO.FileStream(ImageFilePath, IO.FileMode.Open, IO.FileAccess.Read)
        Dim _BinaryReader As New IO.BinaryReader(_FStream)
        _tempByte = _BinaryReader.ReadBytes(Convert.ToInt32(_NumBytes))
        _fileInfo = Nothing
        _NumBytes = 0
        _FStream.Close()
        _FStream.Dispose()
        _BinaryReader.Close()
        Return _tempByte
    Catch ex As Exception
        Return Nothing
    End Try
End Function

Public Function ConvertBytesToMemoryStream(ByVal ImageData As Byte()) As IO.MemoryStream
    Try
        If IsNothing(ImageData) = True Then
            Return Nothing
            'Throw New ArgumentNullException("Image Binary Data Cannot be Null or Empty", "ImageData")
        End If
        Return New System.IO.MemoryStream(ImageData)
    Catch ex As Exception
        Return Nothing
    End Try
End Function

Public Function ConvertImageFiletoMemoryStream(ByVal ImageFilePath As String) As IO.MemoryStream
    If String.IsNullOrEmpty(ImageFilePath) = True Then
        Return Nothing
        ' Throw New ArgumentNullException("Image File Name Cannot be Null or Empty", "ImageFilePath")
    End If
    Return ConvertBytesToMemoryStream(ConvertImageFiletoBytes(ImageFilePath))
End Function

End Class

Answer 4

我在使用 @dMo 先生的程序时遇到问题，它向我显示错误“列‘图片’不能为空”

这是我的代码。

Private Sub ButtonSave_Click(sender As Object, e As EventArgs) Handles ButtonSave.Click
    Dim filename As String = TextBoxSave.Text + ".jpg"
    Dim FileSize As UInt32

    conn.Close()

    Dim mstream As New System.IO.MemoryStream()
    PictureBoxSave.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
    Dim arrImage() As Byte = mstream.GetBuffer()

    FileSize = mstream.Length
    Dim sqlcmd As New MySqlCommand
    Dim sql As String
    mstream.Close()

    sql = ("insert into employeedetails  (picture,filename,filesize) VALUES(@File, @FileName, @FileSize)")

    Try
        conn.Open()
        With sqlcmd
            .CommandText = sql
            .Connection = conn
            .Parameters.AddWithValue("@FileName", filename)
            .Parameters.AddWithValue("@FileSize", FileSize)
            .Parameters.AddWithValue("@File", arrImage)

            .ExecuteNonQuery()
        End With
    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        conn.Close()
    End Try
End Sub

PS 我很抱歉发布这个 adndand 答案，我没有足够的声誉来评论这篇文章

Answer 5

下面的代码在表中插入一条车辆信息记录。所选汽车的图像将转换为内存流并以 Varbinary 形式保存到数据库中。

一个函数用于将图像转换为内存流。

  ' Upload new vehicle image

    Private Sub BtnUpload_Click(sender As Object, e As EventArgs) Handles 
    BtnUpload.Click

    Dim imgBinary As Byte()

    With Me.OpenFileDialog1
        .FileName = ""
        .Filter = "Image Files(*.BMP;*.JPG;*.JEPG;*.GIF)|*.BMP;*.JPG;*.JEPG;*.GIF|All files (*.*)|*.*"
        .RestoreDirectory = True
        .ValidateNames = True
        .CheckFileExists = True
        If .ShowDialog = Windows.Forms.DialogResult.OK Then
            'Me.PicImage.Image.Dispose()
            Me.PicImage.Image = System.Drawing.Image.FromFile(.FileName)
        End If
    End With

    imgBinary = ConvertImage(PicImage.Image)

    Dim command As New SqlCommand("insert into MyCars(CarId, Manufacture, CarModel, CarClass, CarImage) values(@CarId, @Manufacture, @CarModel, @CarClass, @CarImage)", connection)

    command.Parameters.Add("@CarId", SqlDbType.VarChar).Value = CInt(TxtID.Text)
    command.Parameters.Add("@Manufacture", SqlDbType.VarChar).Value = TxtManufacturer.Text
    command.Parameters.Add("@CarModel", SqlDbType.VarChar).Value = TxtModel.Text
    command.Parameters.Add("@CarClass", SqlDbType.VarChar).Value = TxtClass.Text
    command.Parameters.Add("@CarImage", SqlDbType.VarBinary).Value = imgBinary

    Try
        connection.Open()
        If command.ExecuteNonQuery() = 1 Then
            MessageBox.Show("Car # " & TxtID.Text & " successfully added to database.")
        Else
            MessageBox.Show("Car not added!")
        End If

    Catch ex As Exception
        MessageBox.Show("Error while inserting record on table..." & ex.Message, "Insert Records")
    Finally
        connection.Close()
    End Try

End Sub

以下函数将图像转换为内存流。

' Convert Image from Memory Stream
Public Function ConvertImage(ByVal myImage As Image) As Byte()

    Dim mstream As New MemoryStream
    myImage.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)

    Dim myBytes(mstream.Length - 1) As Byte
    mstream.Position = 0

    mstream.Read(myBytes, 0, mstream.Length)

    Return myBytes

End Function

下面的代码用于显示数据库中的图像。使用 ID（整数）来显示图像。

    Private Sub BtnShowImg_Click(sender As Object, e As EventArgs) Handles BtnShowImg.Click

    Dim command As New SqlCommand("select * from MyCars where CarId = @CarId", connection)
    command.Parameters.Add("CarId", SqlDbType.VarChar).Value = TxtID.Text

    Dim table As New DataTable()
    Dim adapter As New SqlDataAdapter(command)

    adapter.Fill(table)

    If table.Rows.Count <= 0 Then

        MessageBox.Show("No Image for the Selected Id")

    Else

        TxtID.Text = table.Rows(0)(0).ToString()                ' Col 0 = CarId
        TxtManufacturer.Text = table.Rows(0)(1).ToString()      ' Col 1 = Manufacturer
        TxtModel.Text = table.Rows(0)(2).ToString               ' Col 2 = Model
        TxtClass.Text = table.Rows(0)(3).ToString()             ' Col 3 = Vehicle Class

        Dim img() As Byte
        img = table.Rows(0)(4)  ' Col 4 = Img

        Dim ms As New MemoryStream(img)

        PicImage.Image = Image.FromStream(ms)

    End If

End Sub

界面 - 希望有帮助