Add support for solar feature tracking

[Jack Ireland]

Solar physicists are often interested in only a subfield of the Sun. Since the Sun rotates, features can move across the disc of the Sun. It would be good to have a feature tracking capability on HV/JHV. Perhaps it work like this - the user picks a point on the disc. As the user steps forward and backwards in time, that point remains in the same location relative to the viewer window. The Sun will appear to rotate underneath that point (which is a feature the user is interested in). HV will have to work out which tiles will have to returned in order to keep the selected feature at the same location in the user window. JHV will have to work out which parts (wavelet coefficients of the sub-region) of the JPEG2000 files will have to returned in order to keep the selected feature at the same location in the user window. Thanks!

[Jack Ireland (jack-ireland)]

Now that hv.org has movie capability I have changed the criticality of this feature request.

[Jack Ireland (jack-ireland)]

Since HEK features and events are being included in Helioviewer.org, this feature has become much more important.

In addition, this feature will allow users to create movies that track features and events across the disk. This can be added as a simple check box in the Movie Settings dialog. There are a couple of cases when tracking might not be offered. The first case is when the whole disk of the Sun is in the viewer window. Tracking of solar features does not make any sense then. The other case is when the user is zoomed out very far. In this case we can assume that the user is looking at data off of the disk of the Sun, so that even if only a part of the disk of the Sun is in the viewer window, there is no need for tracking to be applied.