My company is researching a project that will allow our clients to capture autographs/signatures on a mobile device. The functionality will need to work offline and on any of the major mobile operating systems. These signatures will be stored in a MS SQL Server database and displayed in reports in our main system, which is written in PowerBuilder 12.5. In my research I have found Microsoft's Digital Ink format that is natively supported by PowerBuilder's controls. My question is are there signature capture libraries available for each of the major mobile platforms (Android, iOS, Windows Mobile) that can export signatures to the Digital Ink format? I did some basic googling but didn't find anything.