VBAからGDI+を使う資料集
inet上の達人の方々から御教示いただいたコードを少しアレンジさせてもらっています(切り貼りとも言います)。
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画像ファイル→Picture、GDI+


リサイズしてpictureに変換するコードは別途載せてあるが、commentが参考になるかも

Attribute VB_Name = "modLoadPictureGDI"
'This module provides a LoadPictureGDI function, which can
'be used instead of VBA's LoadPicture, to load a wide variety
'of image types from disk - including png.
'
'The png format is used in Office 2007 to provide images that
'include an alpha channel for each pixel's transparency
'
'Author:    Stephen Bullen
'Date:      31 October, 2006
'Email:     stephen@oaltd.co.uk

Option Explicit

'Declare a UDT to store a GUID for the IPicture OLE Interface
Private Type GUID
    Data1 As Long
    Data2 As Integer
    Data3 As Integer
    Data4(0 To 7) As Byte
End Type

'Declare a UDT to store the bitmap information
Private Type PICTDESC
    Size As Long
    Type As Long
    hPic As Long
    hPal As Long
End Type

'Declare a UDT to store the GDI+ Startup information
Private Type GdiplusStartupInput
    GdiplusVersion As Long
    DebugEventCallback As Long
    SuppressBackgroundThread As Long
    SuppressExternalCodecs As Long
End Type

'Windows API calls into the GDI+ library
Private Declare Function GdiplusStartup Lib "GDIPlus" (token As Long, inputbuf As GdiplusStartupInput, Optional ByVal outputbuf As Long = 0) As Long
Private Declare Function GdipCreateBitmapFromFile Lib "GDIPlus" (ByVal filename As Long, bitmap As Long) As Long
Private Declare Function GdipCreateHBITMAPFromBitmap Lib "GDIPlus" (ByVal bitmap As Long, hbmReturn As Long, ByVal background As Long) As Long
Private Declare Function GdipDisposeImage Lib "GDIPlus" (ByVal image As Long) As Long
Private Declare Function GdiplusShutdown Lib "GDIPlus" (ByVal token As Long) As Long
Private Declare Function OleCreatePictureIndirect Lib "olepro32.dll" (PicDesc As PICTDESC, RefIID As GUID, ByVal fPictureOwnsHandle As Long, IPic As IPicture) As Long


' Procedure:    LoadPictureGDI
' Purpose:      Loads an image using GDI+
' Returns:      The image as an IPicture Object
Public Function LoadPictureGDI(ByVal sFilename As String) As IPicture

    Dim uGdiInput As GdiplusStartupInput
    Dim hGdiPlus As Long
    Dim lResult As Long
    Dim hGdiImage As Long
    Dim hBitmap As Long

    'Initialize GDI+
    uGdiInput.GdiplusVersion = 1
    lResult = GdiplusStartup(hGdiPlus, uGdiInput)

    If lResult = 0 Then

        'Load the image
        lResult = GdipCreateBitmapFromFile(StrPtr(sFilename), hGdiImage)

        If lResult = 0 Then

            'Create a bitmap handle from the GDI image
            lResult = GdipCreateHBITMAPFromBitmap(hGdiImage, hBitmap, 0)

            'Create the IPicture object from the bitmap handle
            Set LoadPictureGDI = CreateIPicture(hBitmap)

            'Tidy up
            GdipDisposeImage hGdiImage
        End If

        'Shutdown GDI+
        GdiplusShutdown hGdiPlus
    End If

End Function


' Procedure:    CreateIPicture
' Purpose:      Converts a image handle into an IPicture object.
' Returns:      The IPicture object
Private Function CreateIPicture(ByVal hPic As Long) As IPicture

    Dim lResult As Long, uPicInfo As PICTDESC, IID_IDispatch As GUID, IPic As IPicture

    'OLE Picture types
    Const PICTYPE_BITMAP = 1

    ' Create the Interface GUID (for the IPicture interface)
    With IID_IDispatch
        .Data1 = &H7BF80980
        .Data2 = &HBF32
        .Data3 = &H101A
        .Data4(0) = &H8B
        .Data4(1) = &HBB
        .Data4(2) = &H0
        .Data4(3) = &HAA
        .Data4(4) = &H0
        .Data4(5) = &H30
        .Data4(6) = &HC
        .Data4(7) = &HAB
    End With

    ' Fill uPicInfo with necessary parts.
    With uPicInfo
        .Size = Len(uPicInfo)
        .Type = PICTYPE_BITMAP
        .hPic = hPic
        .hPal = 0
    End With

    ' Create the Picture object.
    lResult = OleCreatePictureIndirect(uPicInfo, IID_IDispatch, True, IPic)

    ' Return the new Picture object.
    Set CreateIPicture = IPic

End Function