Decode base64 to image in vb.net

Question

I've been searching on the internet and have not found an answer. Would you like to tell me, how to decode from base64 to be Image like line graph? I've been trying to convert from base64 to Byte array first and from Byte array to 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

It would be a good idea to include the error you're getting at that line. — Paul Karam, Mar 27 '18 at 07:56
Base64 is a string, not a Byte(). You'll need to change the function signature and insert Convert.FromBase64String(). If it still fails then the base64 string does not represent a properly encoded image, the way it is encoded in a file on disk. You'll need to document where it came from, or ask the programmer who wrote the code that generated the string. — Hans Passant, Mar 27 '18 at 07:56
@HansPassant: this isi what I code before above: base64decode = rtb_code.Text data = Convert.FromBase64String(base64decode) –‘base64decode is the string rtb2.Text = BitConverter.ToString(data) End Sub And then I call the code above — Winda Sari Elisabeth Siburian, Mar 27 '18 at 09:48

score 5 · Answer 1 · edited Dec 14 '22 at 21:43

Looking at your code, your problem could be using the variable name image instead of something like _image.

Keep in mind that VB is not case sensitive like C# and other programming languages.

In your code, I assume you defined your image variable as Image.

To use the static Image.FromStream(ms), you either need to use the fully qualified name of Image or change your variable name.

Here's how you can fix your code:

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

Or you can do this by changing your variable name, such as:

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

#Update:

You can try to convert the Byte array to Image also by using ImageConvertor:

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

#Update 2:

Since it looks like that the main problem is with the base64 string. Please have a look at my small demo that convert an Image from inside a PictureBox to base64 string, then to Byte array, and at the end, back to an 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

Note that after converting the Image to base64 string, it looks something like that (keep in mind that each image is different, hence you won't get the same string):

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

If you look at the first 5 characters of the string, you notice it's equal to /9j/4 which means that the file represented by this string is a PNG file, you may look at my old answer to see how to validate a base64 string.

Another note, I used a small PNG image, hence I used the next format:

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

If you have another Format and you want to use same code, make sure to change the format.

thanks for your remind me. I've been change my code, but still not work. "Parameter is not valid" in line: _image = Image.FromStream(ms). Do u have any idea? — Winda Sari Elisabeth Siburian, Mar 27 '18 at 09:20
@Paul : Keep in mind that the OP said that the image is base64 encoded. — Visual Vincent, Mar 27 '18 at 09:35
@VisualVincent OP also said that the base64 string is being converted to byte array then to Image. So if that doesn't work, then Either the base64 is not well converted to byte array or it's not well converted from image to base64 in first place. I tried all those snippets I posted here before I do that. — Paul Karam, Mar 27 '18 at 09:39
@PaulKaram this is: AAAAAAABBAoZMliFs9Xk4NC7qZ+bnaOtucjX5O/3+/v27N3MuaeWh3hrYFdQSkdDQD06ODc2Njc3ODc3NjQzMTAvLi0rKSclIyEfHhwaGBYUEhEPDg0MCwoJCAgHBwYFBAQDAwICAgICAgEBAQAAAAAAAAAAAAAAAAAAAAAAAAA= — Winda Sari Elisabeth Siburian, Mar 27 '18 at 09:56
At first sight, that doesn't look like a valid image format base64 string. Your problem could be from the way that base64 has been generated. — Paul Karam, Mar 27 '18 at 10:12
@WindaSariElisabethSiburian Can you post how are you converting the image to base64 then to byte array? — Paul Karam, Mar 27 '18 at 11:32
@Paul : True, it depends on how she converts it to a byte array. The first time I read it I got the feeling that she was converting _the string itself_ to `Byte()` and not from base64 to `Byte()`, but I'm probably wrong. :) — Visual Vincent, Mar 27 '18 at 16:48
@PaulKaram : I didn't convert image to base64,but it's generated from a device. — Winda Sari Elisabeth Siburian, Mar 28 '18 at 02:19
@WindaSariElisabethSiburian Then most likely, it's not generated in a good way, or it's not an image at all. Anyways, I would suggest you also try to convert the base64 string to Image instead of converting it to byte array first. — Paul Karam, Mar 28 '18 at 04:17
@PaulKaram hm, but I'm sure that it will be an image. And if it's not generated in a good way, then error should be about base64 not in my code so it shows 'parameter is not valid'. (I hope you get what I said) — Winda Sari Elisabeth Siburian, Mar 28 '18 at 04:21
@WindaSariElisabethSiburian That's what I mean. I did create a small demo containing an image. I converted the image to base64, then to Byte array, then I converted it to image again using your code and it worked. So basically the error is within the base64 string. — Paul Karam, Mar 28 '18 at 04:23
o ya? i'll try like you did, Sir! thank for your all help. :) — Winda Sari Elisabeth Siburian, Mar 28 '18 at 04:27
@WindaSariElisabethSiburian Please take a look at the part `Update 2` of my answer. — Paul Karam, Mar 29 '18 at 05:30

Decode base64 to image in vb.net

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