test.cs

var signatureImage = System.Text.Encoding.UTF8.GetString(
               Convert.FromBase64String(data.SignatureImage));

var stamp = TXTextControl.Esign.SignatureStamp.Create(
   new Size(600, 250),
   data.Name,
   12, 
   signatureImage,
   data.UniqueId,
   Color.LightGray,
   Color.Magenta,
   80, 12, 10);

// create a memory stream from SVG
using (MemoryStream ms = new MemoryStream(
   stamp, 0, stamp.Length, writable: false, publiclyVisible: true)) {

   foreach (SignatureField field in tx.SignatureFields) {
      field.Image = new SignatureImage(ms);
   }
}