Numerous different .std files exists, so there might actually be more than one std to jpeg conversion. Typically searched for the export of graphics, so the most probable reason for such export would be export of OpenOffice.org drawing templates (.std) to JPEG format, which you can using any of the 'Draw' apps from various OpenDocument based productivity suites, such as OpenOffice.org or LibreOffice.
Updated: July 25, 2023