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Convert Base64 string to jpeg

Posted on 2014-10-28
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Last Modified: 2014-10-28
How would I convert a base64 png encoded string to a jpeg image and then save the jpeg to sql 2008 image field?  The code below
results in a black square!

my code:

dim txt as string ="data:image/png;base64,iVBORw0KGgoAA etc......" ' <---this is a shortened version of a true base64 string

Dim ms As New MemoryStream(Convert.FromBase64String(txt))
           
Dim bmp As Bitmap = Bitmap.FromStream(ms) <---load bitmap from memory stream


            'create new memory stream
            Dim jpgms As New MemoryStream()
            jpgms.Position = 0
            bm.Save(jpgms, System.Drawing.Imaging.ImageFormat.Jpeg) <---convert to jpeg


jpgms.toArray() <--used as data source for sql 2008 image
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Question by:JoeBo747
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4 Comments
 
LVL 35

Expert Comment

by:Robert Schutt
ID: 40408943
You need to get rid of the header. Try something like this:
        Dim txt As String = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==" ' red dot from wikipedia
        If txt.StartsWith("data:") Then
            Dim poscomma As Integer = txt.IndexOf(",") + 1
            txt = txt.Substring(poscomma, txt.Length - poscomma)
        End If

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Author Comment

by:JoeBo747
ID: 40409119
Hi Robert,
Thanks for your reply,  the code supplied was copied accross from a trial app which does remove the header, sorry for the confusion.
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LVL 35

Accepted Solution

by:
Robert Schutt earned 500 total points
ID: 40409727
Ok, so could you post the entire base64 string or is the image sensitive?

I tested with the following code which simply puts the image in a picturebox on a form, if you could test that, then at least we could probably assume the problem is in the database code in which case I would ask you to post a bit more of your code regarding that part of the program.
Imports System.IO

Public Class Form1
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Try
            Dim txt As String = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==" ' red dot from wikipedia
            If txt.StartsWith("data:") Then
                Dim poscomma As Integer = txt.IndexOf(",") + 1
                txt = txt.Substring(poscomma, txt.Length - poscomma)
            End If

            Dim ms As New MemoryStream(Convert.FromBase64String(txt))

            Dim bm As Bitmap = Bitmap.FromStream(ms) '<---load bitmap from memory stream

            'create new memory stream
            Dim jpgms As New MemoryStream()
            jpgms.Position = 0
            bm.Save(jpgms, System.Drawing.Imaging.ImageFormat.Jpeg) '<---convert to jpeg

            PictureBox1.Image = Image.FromStream(jpgms)

            'jpgms.toArray() '<--used as data source for sql 2008 image
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class

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Author Closing Comment

by:JoeBo747
ID: 40409979
Hi Robert,

Thanks for your assistance,
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