vba - Using base64 data stored in CustomXMLPart as image in Office

Question

As a followup to this question about using images stored in an Excel file on a button in the ribbon:

Is it possible to use an image stored in a CustomXMLPart/CustomXMLNode in base64-encoded string as an image in an Office document without first saving it to disk and loading it back?

The place where I want to use the image takes an IPictureDisp object as a parameter (like the LoadPicture function returns, but that will only load files from disk).

Answer 1

First you need to convert your base_64 data to byte array:

Private Function decodeBase64(ByVal strData As String) As Byte()
    Dim objXML As MSXML2.DOMDocument
    Dim objNode As MSXML2.IXMLDOMElement

    Set objXML = New MSXML2.DOMDocument
    Set objNode = objXML.createElement("b64")
    objNode.DataType = "bin.base64"
    objNode.Text = strData
    decodeBase64 = objNode.nodeTypedValue

    Set objNode = Nothing
    Set objXML = Nothing
End Function

from: http://thydzik.com/vb6vba-functions-to-convert-binary-string-to-base64-string/

then you can load it in memory and create your IPictureDisp using information on this topic: http://www.xtremevbtalk.com/showthread.php?t=137857

Type GUID
  Data1 As Long
  Data2 As Integer
  Data3 As Integer
  Data4(7) As Byte
End Type

Private Declare Function CreateStreamOnHGlobal Lib "ole32.dll" (ByRef hGlobal As Any,     ByVal fDeleteOnResume As Long, ByRef ppstr As Any) As Long
Private Declare Function OleLoadPicture Lib "olepro32.dll" (ByVal lpStream As IUnknown, ByVal lSize As Long, ByVal fRunMode As Long, ByRef riid As GUID, ByRef lplpObj As Any) As Long
Private Declare Function CLSIDFromString Lib "ole32.dll" (ByVal lpsz As Long, ByRef pclsid As GUID) As Long

Private Const SIPICTURE As String = "{7BF80980-BF32-101A-8BBB-00AA00300CAB}"

Public Function PictureFromArray(ByRef b() As Byte) As IPicture
  On Error GoTo errorhandler

  Dim istrm As IUnknown
  Dim tGuid As GUID

  If Not CreateStreamOnHGlobal(b(LBound(b)), False, istrm) Then
    CLSIDFromString StrPtr(SIPICTURE), tGuid
    OleLoadPicture istrm, UBound(b) - LBound(b) + 1, False, tGuid, PictureFromArray
  End If

  Set istrm = Nothing
  Exit Function
errorhandler:
  Debug.Print "Could not convert to IPicture!"
End Function