mysql - 使用vb检索数据库mysql中的图像

Question

我想在vb中不使用id从数据库mysql中检索图像。但为什么我有错误“无法将类型为‘System.Byte[]’的对象转换为类型为‘System.Drawing.Image’。”

这是我的编码。我正在使用 Visual Basic 2008 和数据库 mysql。图片格式为BLOB。例如。[BLOB - 22.1 KiB]

Imports MySql.Data.MySqlClient
Imports System.Drawing.Imaging
Public Class Form_Popup

    Private Sub Form_Popup_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        objconn = New MySqlConnection("server=localhost;database=new;userid=root;password= 'root'")
        objconn.Open()
        strsql = "select * from peribadi where Noid =@field1"
        command = (New MySql.Data.MySqlClient.MySqlCommand(strsql, objconn))
        With command
            .Parameters.AddWithValue("@field1", FormRegister.TextBox1.Text)
        End With

        objdr = command.ExecuteReader
        If (objdr.Read()) Then
            Label4.Text = (objdr("Name"))
            Label5.Text = (objdr("Address"))
            PictureBox1.Image = (objdr("picture"))

        End If

    End Sub

Answer 1

检索您的图像时出现错误。您需要先将图像转换为字节数组。在将其显示到图片框之前..

 Public Function ResizeImageWithAspect(ByVal picImage As Image, ByVal newWidth As Integer) As Bitmap
    Dim original As Image = picImage
    If Not original Is Nothing Then
        //Find the aspect ratio between the height and width.
        Dim aspect As Single = CSng(original.Height) / CSng(original.Width)

        //Calculate the new height using the aspect ratio
        // and the desired new width.
        Dim newHeight As Integer = CInt((newWidth * aspect))

        //Create a bitmap of the correct size.
        Dim temp As New Bitmap(newWidth, newHeight, original.PixelFormat)

        //Get a Graphics object from the bitmap.
        Dim newImage As Graphics = Graphics.FromImage(temp)

        //Draw the image with the new width/height
        newImage.DrawImage(original, 0, 0, newWidth, newHeight)

        //Dispose of our objects.
        Return temp
        original.Dispose()
        temp.Dispose()
        newImage.Dispose()
    Else
        Return Nothing
    End If

End Function

Public Function ByteToImage(ByVal blob() As Byte) As Bitmap
    Dim mStream As New System.IO.MemoryStream
    Dim pData() As Byte = DirectCast(blob, Byte())
    mStream.Write(pData, 0, Convert.ToInt32(pData.Length))
    Dim bm As Bitmap = New Bitmap(mStream, False)
    mStream.Dispose()
    Return bm
End Function

Public Function FileImageToByte(ByVal filePath As String) As Byte()
    Dim fs As FileStream = New FileStream(filePath, FileMode.Open, FileAccess.Read)
    Dim br As BinaryReader = New BinaryReader(fs)
    Dim bm() As Byte = br.ReadBytes(fs.Length)
    br.Close()
    fs.Close()
    Dim photo() As Byte = bm
    Return photo
End Function

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