Option to draw cross-hairs on a track preview window

[smarquard]

For camera calibration purposes (for example with LectureSight) it would be quite helpful to be able to draw crosshairs on a track preview (typically presenter) so you can see the vertical and horizontal centres.

[paulgration]

We did exactly this as part of a bigger project/plugin some time ago using the rsvgoverlay from gstreamer although not for calibration purposes...we had a requirement to provide crosshairs on top of the preview so that users of a specific type of space (self service recording studio) have a target to look at on a teleprompter to ensure they're looking at the camera behind it when making recordings.
I've recently been reworking it, when time permits, to use cairooverlay (plugins-good) instead of rsvgoverlay (plugins-bad).

Here's a gist I just put together (adapted from my experiments before) which I just put some crosshairs on - should be fairly easy to turn into a calibration plugin, I might have a look at doing that when I get time unless someone else gets there in the meantime.

[paulgration]

@smarquard are you able to give this a try at some stage? It specifically targets presenter flavors (as I couldn't think of a reason why you would want to add crosshairs to anything else), if all works as expected I'll put it forward to be added to the list of Galicaster plugins.