c# - 如何将二进制数据转换为图像并在图片框中显示它们？

Question

我在访问文件中有一个图像，我想使用用户 ID 在另一个 Windows 窗体窗体中检索并显示它。

保存图像的代码：

 Dim img = PictureBox1. Image

 Dim ms As New System.IO.MemoryStream
 img.Save(ms, img.RawFormat)
 img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg)
 bytImage = ms.ToArray()
 ms.Close()

检索图像的代码：

 con.ConnectionString = dbProvider & dbSource

 con.Open()
 Dim userIdPro = Transfer.userIdPro
 Dim query = ("SELECT Image FROM User_info WHERE ID = " & userIdPro & ";")

 Dim ds As New DataSet

 Dim dr As OleDb.OleDbDataReader
 Dim cm = New OleDb.OleDbCommand(query, con)
 dr = cm.ExecuteReader
 While dr.Read()
     Dim MyByte = dr.Item("Value")
     Dim fs = New MemoryStream
     fs.Write(MyByte, 0, MyByte.Length)
     fs.Flush()
     Dim MyImg = Image.FromStream(fs, True)
     MyImg.Save(dr.Item("ID").ToString & ".JPG", System.Drawing.Imaging.ImageFormat.Jpeg)
        PictureBox1.Image = MyImg
        fs.Close()
        fs = Nothing
     End While
     con.Close()
End Sub

我无法将二进制数据带入dr；它总是空的。

标签： c#vb.netwinforms

Answer 1

我把你的代码调用函数 bytesToImage(...)`。您不需要将图像保存在本地，除非您有理由这样做。

 con.ConnectionString = dbProvider & dbSource

 con.Open()
 Dim userIdPro = Transfer.userIdPro

 // Don't concatenate your parameters. This is a bad practice and
 // exposes your application to SQL injection attacks. Use SQL
 // parameters instead.

 Dim query = ("SELECT Image FROM User_info WHERE ID = " & userIdPro & ";")

 Dim ds As New DataSet

 Dim dr As OleDb.OleDbDataReader
 Dim cm = New OleDb.OleDbCommand(query, con)
 dr = cm.ExecuteReader
 While dr.Read()

     Dim MyByte = dr.Item("Value")
     Dim MyImg As Image

     If MyByte IsNot Nothing Then
        // You do not need to save it, just convert to an image
        // type and set it to your PictureBox1 control.

        MyImg = bytesToImage(MyByte)
        PictureBox1.Image = MyImg
     End If
End While
con.Close()

您的班级应该具有以下Image属性Byte()

<Table("User_info")>
Public Class User

   Public Property Photo As Byte()

End Class

使用以下功能：

Public Function imageToBytes(ByVal imageIn As System.Drawing.Image) As Byte()
    Dim ms As MemoryStream = New MemoryStream()
    imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg)
    Return ms.ToArray()
End Function

Public Function bytesToImage(ByVal byteArrayIn As Byte()) As Image
    Dim ms As MemoryStream = New MemoryStream(byteArrayIn)
    Dim returnImage As Image = Image.FromStream(ms)
    Return returnImage
End Function

要将图像保存到数据库中：

Public Sub SaveImage()
    Using context = New ProjectDb()
        Dim user = New User() With {
            .Id = Guid.NewGuid,
            .Photo = imageToBytes(PictureBox1.Image)
        }
        context.Users.Add(user)
        context.SaveChanges()
    End Using
End Sub

要从数据库中获取图像：

Public Function GetImage(ByVal id As Guid) As Image
    Using context = New ProjectDb()

        Dim image As Image

        Dim user As User = context.Users.FirstOrDefault(Function(x) x.Id = id)

        If user IsNot Nothing Then
            image = bytesToImage(user.Photo)
            PictureBox2.Image = image
        End If

    End Using
End Function