在vb.net中将base64解码为图像

Question

我一直在互联网上搜索，但没有找到答案。你想告诉我，如何解码base64为Image折线图吗？我一直在尝试先从数组转换base64为Byte数组，然后从Byte数组转换为Image.

Private Function convertbytetoimage(ByVal BA As Byte())
     Dim ms As MemoryStream = New MemoryStream(BA)
     image = Image.FromStream(ms) 'I always get wrong in this line.
     Return image
 End Function

Answer 1

查看您的代码，您的问题可能是使用变量名称image而不是_image.

请记住，VB不像 C# 和其他编程语言那样区分大小写。

在您的代码中，我假设您将image变量定义为Image.

要使用 static Image.FromStream(ms)，您需要使用 的完全限定名称Image或更改变量名称。

以下是修复代码的方法：

Private Function convertbytetoimage(ByVal BA As Byte())
    Dim ms As MemoryStream = New MemoryStream(BA)
    image = System.Drawing.Image.FromStream(ms)
    Return image
End Function

或者您可以通过更改变量名称来完成此操作，例如：

Dim _image as Image

Private Function convertbytetoimage(ByVal BA As Byte())
    Dim ms As MemoryStream = New MemoryStream(BA)
    _image = Image.FromStream(ms)
    Return _image
End Function

＃更新：

您可以尝试使用以下方法将数组转换Byte为：ImageImageConvertor

Private Function convertbytetoimage(ByVal BA As Byte())
    Dim converter As ImageConverter = New ImageConverter()
    _image = CType(converter.ConvertFrom(BA), Image)
    Return _image
End Function

#更新2：

因为看起来主要问题在于字符串base64。请看一下我的小演示，它将Imagea 内部的an 转换PictureBox为base64字符串，然后转换为Byte数组，最后再转换回Image.

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    Dim base64String = ConvertImageToBase64String() 'Using Functions To Make the code tidier
    Dim byteArray = ConvertBase64ToByteArray(base64String) 'Using Functions To Make the code tidier
    Dim image = convertbytetoimage(byteArray) 'Using Functions To Make the code tidier
    PictureBox2.Image = image 'since we're using a small windows form app, we'll set back the image to a second picture box.
End Sub

Public Function ConvertImageToBase64String() As String
    Using ms As New MemoryStream()
        PictureBox1.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Png) 'We load the image from first PictureBox in the MemoryStream
        Dim obyte = ms.ToArray() 'We tranform it to byte array..

        Return Convert.ToBase64String(obyte) 'We then convert the byte array to base 64 string.
    End Using
End Function

Public Function ConvertBase64ToByteArray(base64 As String) As Byte()
    Return Convert.FromBase64String(base64) 'Convert the base64 back to byte array.
End Function

'Here's the part of your code (which works)
Private Function convertbytetoimage(ByVal BA As Byte())
    Dim ms As MemoryStream = New MemoryStream(BA)
    Dim image = System.Drawing.Image.FromStream(ms)
    Return image
End Function

请注意，将 转换Image为base64字符串后，它看起来像这样（请记住每个图像都是不同的，因此您不会得到相同的字符串）：

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

如果您查看字符串的前 5 个字符，您会发现它等于，这/9j/4意味着该字符串表示的文件是一个PNG文件，您可以查看我的旧答案以了解如何验证字符串base64。

另请注意，我使用了小PNG图像，因此我使用了下一个格式：

PictureBox1.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Png) 

如果您有其他格式并且想要使用相同的代码，请确保更改格式。