Dim img As New ImageList
img.ImageSize = New Size(200, 200)  'Bildgröße
 
Dim picext As String() = New String() _
{"*.bmp", "*.jpg", "*.gif", "*.tif", "*.png"}
 
Dim sourcepath As String = "F:\demo\in"
 
'Bilder aus einem Verzeichnis in die Liste laden 
For Each file As String In My.Computer.FileSystem.GetFiles _
(sourcepath, FileIO.SearchOption.SearchTopLevelOnly, picext)
 
   Using bmp As New Bitmap(file)
     Dim filename As String = IO.Path.GetFileName(file)
     img.Images.Add(filename, CType(bmp.Clone, Image))
   End Using
 
Next file
 
Dim destinationpath As String = "F:\demo\out"
 
'Bilder in einem Verzeichnis speichern (Überschreiben)
For Each filename As String In img.Images.Keys
 
    Dim filepath As String = IO.Path.Combine(destinationpath, filename)
    img.Images(filename).Save(filepath, GetPicFormat(IO.Path.GetExtension( _
      filepath)))
 
Next filename

Private Function GetPicFormat(ByVal extension As String) As Imaging.ImageFormat
    'Einige Beispiele
    extension = extension.ToUpper.Trim
    If extension = ".GIF" Then Return Imaging.ImageFormat.Gif
    If extension = ".JPG" Then Return Imaging.ImageFormat.Jpeg
    If extension = ".TIF" Then Return Imaging.ImageFormat.Tiff
    If extension = ".PNG" Then Return Imaging.ImageFormat.Png
    Return Imaging.ImageFormat.Bmp
End Function