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

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