Undo and Redo

                _bmViewer.Bitmap.UndoRedoEnabled = False

                'Dim UserImage As Aurigma.GraphicsMill.Bitmap = _bmViewer.Bitmap

                Dim UserImage As New Aurigma.GraphicsMill.Bitmap(_bmViewer.Bitmap)

                Dim _item As Aurigma.GraphicsMill.WinControls.ThumbnailListItem
                _item = _thlMask.SelectedItems(0)

                Dim MaskImage As New Aurigma.GraphicsMill.Bitmap(_item.Pidl.Path)
                Dim resultImage As New Aurigma.GraphicsMill.Bitmap(UserImage.Width, UserImage.Height, Aurigma.GraphicsMill.PixelFormat.Format32bppArgb)

                ' Mask Preperation
                MaskImage.HorizontalResolution = UserImage.HorizontalResolution
                MaskImage.VerticalResolution = UserImage.VerticalResolution
                MaskImage.Transforms.Resize(UserImage.Width, UserImage.Height, Transforms.ResizeMode.Resize)
                If MaskImage.PixelFormat <> PixelFormat.Format8bppGrayScale Then
                    MaskImage.ColorManagement.Convert(PixelFormat.Format8bppGrayScale)
                End If

                resultImage.HorizontalResolution = UserImage.HorizontalResolution
                resultImage.VerticalResolution = UserImage.VerticalResolution
                resultImage.Transforms.Resize(UserImage.Width, UserImage.Height, Transforms.ResizeMode.Resize)


                resultImage = ManualCombine(UserImage, MaskImage)


                _bmViewer.Bitmap = resultImage
                _bmViewer.Bitmap.UndoRedoEnabled = True
                _bmViewer.Bitmap.SaveState()
                _btnUndo.Enabled = True