Display Image from Binary data without writing to file

**Movian** · 10-14-2014, 07:02 AM

Hey,
so due to some new security requirements we are no longer allowed to store files on the file system and reference the location. We have to store the files in the database itself.....

I have implemented a setup that will allow me to import and export binary files to and from a database table varbinary(max) field...

however some of these items I would like to be able to have the user view without writing to a file again... for example if they store a png or gif image I would like to be able to retrieve the binary data and push that to an image control to show the file on the form without writing the image to disk then pointing the image control at that location.

down the road I would also like to be able to do this with PDF files but one step at a time.

As always any help/ suggestions / links are appreciated.

**Movian** · 10-14-2014, 02:45 PM

as always after I post I don't just stop looking!

Still not there but have some progress, I had a brain wave and added a Microsoft Webbrowser ActiveX control to my form and with a little research I discovered this page

http://ben.lobaugh.net/blog/33713/us...-image-in-html

which provides information on displaying images from Base64 stings, after a little more research I discovered this set of functions

http://thydzik.com/vb6vba-functions-...base64-string/

which should let me convert the binary string I get from the following functions

Function ReadBinaryFile(filename)  Const adTypeBinary = 1
  
  'Create Stream object
  Dim BinaryStream
  Set BinaryStream = CreateObject("ADODB.Stream")
  
  'Specify stream type - we want To get binary data.
  BinaryStream.Type = adTypeBinary
  
  'Open the stream
  BinaryStream.Open
  
  'Load the file data from disk To stream object
  BinaryStream.LoadFromFile filename
  
  'Open the stream And get binary data from the object
  ReadBinaryFile = BinaryStream.Read
End Function
Function ImportFile(BinaryData, filename As String, FileType As String)  
  Dim SQL As String
  Dim Conn As ADODB.Connection
  Dim RS As ADODB.Recordset
  'Create SQL command To retrieve data
  SQL = "SELECT * FROM tblFileStore WHERE 1=0"
  
  'Get connection To SQL database
  Set Conn = CurrentProject.Connection
  Set RS = CreateObject("ADODB.Recordset")
  RS.Open SQL, Conn, adOpenKeyset, adLockOptimistic, adCmdText
  
  'AddNew - new row To the recordset
  RS.AddNew
  
  'Set source BinaryData To BinaryColumn
  RS("FileData") = BinaryData
  RS("MedicalID") = Forms("frmMain").MedicalID
  RS("FileName") = filename
  RS("FileTYpe") = FileType
  RS("CreationDate") = Date
  
  'Use this code instead of previous line For ORACLE.
  'RS("BinaryColumn").AppendChunk BinaryData
  'Store data To database
  RS.Update


  'Or using one-row AddNew only - instead of AddNew + Update
  'RS.AddNew Array("BinaryColumn", "Description"), _
  '   Array(BinaryData, Description)
  
  'Get an ID of currently added row.
  ImportFile = RS("FileID")
End Function

So I have the binary data available and the functions ready but am having some problems implementing the solution.....

I have implemented the following on a listbox double click (to select the file to display)

Private Sub LstFiles_DblClick(Cancel As Integer)If Not IsNull(Me.LstFiles) And Not Me.LstFiles = "" Then
    Dim myrs As New ADODB.Recordset
    Dim Stream As String
    
    
    myrs.Open "SELECT * FROM tblFileStore WHERE FIleid = '" & Me.LstFiles & "'", CurrentProject.Connection, adOpenKeyset, adLockReadOnly
    Stream = "<Html><head></head><body>"
    Stream = Stream & "<img srv='data:image/" & myrs("filetype") & ";base64," & encodeBase64(bin2Byte(myrs("FileData"))) & "'>"
    Stream = Stream & "</body></html>"
    
    Me.FileBrowser.Document.Open
    Me.FileBrowser.Document.Write Stream
    Me.FileBrowser.Document.Close
    Me.FileBrowser.Refresh
    On Error Resume Next
        myrs.Close
        Set myrs = Nothing
    On Error GoTo 0
End If
End Sub

however this produces an error at the following line in bin2byte - Type mismatch

bytes(byteCount) = bytes(byteCount) + CLng(Mid$(sByte, 8 - i, 1)) * 2 ^ i

the image being used is a Gif image

just trying to slot together the last pieces of this puzzle!

**Movian** · 10-15-2014, 06:39 AM

Ok so baby steps

have taken a step further and have the image displaying on the screen! the secret aparently was that I needed to setup an adodb.stream to handle the data coming back out of the varbinary(max) field.

have one small problem remaining though....

The following code will work, however it writes a copy of the file to disk (I was doing testing) binarystream.savefile myrs("Filedata") this then allows binarystream.read to function and pushes the data to the base64 encoding system that then outputs the correct format for displaying in HTML.

HOWEVER if I remove the file write line.... the binarystream.read returns nothing.... not sure why but as it stands the way I have it laid out the filesave seems to do something important to allow me to read the data correctly from the binary stream... as the whole point of the exercise is to display the file WITHOUT writing a file to disk this posses a problem.

Private Sub LstFiles_DblClick(Cancel As Integer)If Not IsNull(Me.LstFiles) And Not Me.LstFiles = "" Then
    Dim myrs As New ADODB.Recordset
    Dim Stream As String, ImageData As String
    Dim binaryStream As New ADODB.Stream
    
    myrs.Open "SELECT * FROM tblFileStore WHERE FileID = '" & Me.LstFiles & "'", CurrentProject.Connection, adOpenKeyset, adLockReadOnly
    
    'Specify stream type - we want To save binary data.
    binaryStream.Type = adTypeBinary
    
    'Open the stream And write binary data To the object
    binaryStream.Open
    binaryStream.Write myrs("FileData")
    
    binaryStream.SaveToFile "C:\"
    'Start HTML generation
    Stream = "<Html><head></head><body>"
    Stream = Stream & "<img src=" & """" & "data:image/" & myrs("filetype") & ";base64," & encodeBase64(binaryStream.Read) & """" & ">"
    Stream = Stream & "</body></html>"
    
    Me.FileBrowser.Document.Open
    Me.FileBrowser.Document.Write Stream
    Me.FileBrowser.Document.Close
    Me.FileBrowser.Refresh
    On Error Resume Next
        myrs.Close
        Set myrs = Nothing
    On Error GoTo 0
    
    binaryStream.Close
End If
End Sub

I did also change to different functions for encoding the binary data.

Private Function encodeBase64(bytes)  Dim DM, EL
  Set DM = CreateObject("Microsoft.XMLDOM")
  ' Create temporary node with Base64 data type
  Set EL = DM.createElement("tmp")
  EL.DataType = "bin.base64"
  ' Set bytes, get encoded String
  'Convert byte string to byte array
  
  EL.nodeTypedValue = bytes
  encodeBase64 = EL.text
End Function
  
Private Function decodeBase64(base64)
  Dim DM, EL
  Set DM = CreateObject("Microsoft.XMLDOM")
  ' Create temporary node with Base64 data type
  Set EL = DM.createElement("tmp")
  EL.DataType = "bin.base64"
  ' Set encoded String, get bytes
  EL.text = base64
  decodeBase64 = EL.nodeTypedValue
End Function

**Movian** · 10-15-2014, 07:18 AM

Ok after MORE research it appears that after a write to the stream the current position is left at the end of the stream for some reason..... so when you use the read command it reads from the current possition and gets nothing ... because its at the end.

replacing the binarystream.savetofile line with the following

binarystream.position = 0

resolved the problem as this sets the current position back to the start of the stream and allows the read to go from that position.

Hope this will help someone else in the future!!! ^_^

Thread: Display Image from Binary data without writing to file

Thread Tools

Display

Display Image from Binary data without writing to file

Posting Permissions