PowerPoint 在使用 VBA 插入的 .png 图像上留下蓝色背景

问：

我有这个插入图像的powerpoint宏的片段：

Sub InsertRandomPictures()
    Dim fso As Object
    Dim folder As Object
    Dim file As Object
    Dim pptSlide As Slide
    Dim pic As shape
    Dim folderPath As String
    Dim randomWidth As Single, randomHeight As Single
    Dim aspectRatio As Single
    Dim tempPic As shape
    Dim counter As Integer
    
    ' Set the path to the folder containing the pictures
    folderPath = "my/path/to/folder"
    
    ' Set up FileSystemObject
    Set fso = CreateObject("Scripting.FileSystemObject")
    Set folder = fso.GetFolder(folderPath)
    
    ' Reference slide 2
    Set pptSlide = ActivePresentation.Slides(2)
    
    ' Loop through each file in the folder
    For Each file In folder.Files
        ' Check if the file is a picture by looking at its extension
        If LCase(Right(file.Name, 3)) = "jpg" Or LCase(Right(file.Name, 3)) = "png" Or LCase(Right(file.Name, 3)) = "gif" Then        
            
            ' Insert the picture onto slide 2
            Set pic = pptSlide.Shapes.AddPicture( _
                fileName:=folderPath & file.Name, _
                LinkToFile:=msoFalse, _
                SaveWithDocument:=msoTrue, _
                Width:= 100, _
                Height:= 100)
                
            ' Set a random transparency value
            pic.Fill.Transparency = Rnd() * 0.9         
        End If
    Next file
End Sub

但是，它使我的 .png 图像和 .gif 具有透明性，并带有这种丑陋的蓝色填充。当我手动插入同一张图片时，它看起来不错。

我该如何摆脱它？