How do I convert an ODF file to a jpg for publishing on a web page?
I can only recommend that you zoom in on your view as large as possible. Then take a screenshot and save it as a jpg.
If you don’t mind an intermediary step, all those file formats could be saved/printed as PDF, which there exist plenty of ways of converting to JPEG, PNG or other formats.
You didn’t tell the type of the ODF file (e.g. Writer = .odt, Calc = .ods, …).
For Writer, only the first page can be exported to JPEG, File → Export, then select JPEG.
For Calc, either the first page of the first sheet; or the selected cell range, for which activate the Selection checkbox in the file export dialog. Be aware that the resulting image can get huge with a large selection.
For Draw and Impress, direct export of a page to an image format is possible.