Get SPUser from Pserson or Group Column

SPUser GetSPUser(SPField field, object value)
{
 SPFieldUser userField = field as SPFieldUser;
 if (userField == null) return null;
 SPFieldUserValue fieldValue = userField.GetFieldValue(value as string) as SPFieldUserValue;
 if (fieldValue == null) return null;
 SPUser user = fieldValue.User;
 return user;
}