import Microsoft.Ink.Dll

Code:
Dim sc As StrokeCollection = ink1.Strokes
            Dim inkData As Byte() = Nothing
            Using inkMemStream As New MemoryStream
                sc.Save(inkMemStream)
                inkData = inkMemStream.ToArray()
            End Using
            Dim gifData As Byte() = Nothing
            Using ink2 As New Microsoft.Ink.Ink()
                ink2.Load(inkData)
                gifData = ink2.Save(Microsoft.Ink.PersistenceFormat.Gif)
            End Using
            File.WriteAllBytes("c://strokes.gif", gifData)