A utility that would detect parallel (vertical) lines and/or a horizon

In order to automatically "Level" or straighten the horizon of a panorama, it is necessary to assign (2 or more) vertical line control points. It is also possible to assign a horizontal line control point to the horizon, if there is a linear horizon visible (note that horizons are only useful for this when you have a sea view, so detecting horizontal lines isn't critical). This project was started last year as part of the 'lens calibration' project but it is in an unfinished state.

This tool would need to work within the Hugin GUI and as a command-line tool. While we can't expect this to be 100% reliable, it is reasonable to think that something that is far more than 50% reliable could be created for panoramas that exist in man-made environments (where a lot of vertical lines exist) or landscapes (where there is a clear horizontal line denoting the horizon)