Cacher is the code snippet organizer for pro developers

' For complete examples and data files, please go to https://github.com/groupdocs-watermark/GroupDocs.Watermark-for-.NET
Using doc As CellsDocument = Document.Load(Of CellsDocument)("D:\test.xlsx")
    ' Initialize image or text watermark
    Dim watermark As New TextWatermark("Protected image", New Font("Arial", 8))
    watermark.HorizontalAlignment = HorizontalAlignment.Center
    watermark.VerticalAlignment = VerticalAlignment.Center
    watermark.RotateAngle = 45
    watermark.SizingType = SizingType.ScaleToParentDimensions
    watermark.ScaleFactor = 1

    For Each worksheet As CellsWorksheet In doc.Worksheets
        For Each shape As CellsShape In worksheet.Shapes
            If shape.Image IsNot Nothing Then
                ' Add watermark to the image
                shape.Image.AddWatermark(watermark)
            End If
        Next
    Next

    doc.Save()
End Using