[ptx] autopano: first attempt at semi-automatic panorama stitching

[Pablo d'Angelo]

On Wed, 31 Dec 2003, Ed Wildgoose wrote:

I have an implementation that creates a .pto file from a given series of
images, however, currently only 1/2 of the pairs are matched properly.
For the other half, the phase correlation screws up, and the Lucas Kanade
tracker doesn't have a valid estimate. My model is currently based on simple
translations, not on projective transformations.

I have asked the authors of the phase correlation and the tracking code (its
not gpl'ed) if I'm allowed to include it into hugin, but haven't gotten an
answer yet. I'm not sure if I should add it to the main hugin cvs.

> My *guess* is that this will work extremely well for most panoramas with 
> 28mm lenses and above, but do you think that it will work well for 8mm 
> fish eye scenes, or even just very wide angle lenses?

It probably won't work with these. It also has some problems with "normal"
panos, the phase correlation is not working as nicely as I thought.

> I wonder if you could *assume* something like a grid layout and 
> pre-process each image pair based on expected geometry and then apply 
> phase correlation.  eg if you expect the images to be either left or 
> right aligned then coursely correct for an assumed 30% overlap, and go 
> with that.  At least that way the images are roughly capable of being 
> lined up?

The pase correlation is quite fast, and can be applied to whole images as
well. I suspect the problem with the phase correlation implementation I'm
using is that it windows the image, throwing away a huge amount of border
information. It would work better to correlate only the assumed overlaps.

> Along the same vein, perhaps there is some mileage in subdividing an 
> image up into thirds down each axis, precorrecting based on an assumed 
> lens focal length and then phase correlate all 9 pieces against 
> everything else...  The intention would be to catch corner matches and 
> the like..

Hmm, have to think about that.

> 
> Just a wild idea.  Sorry if it's noise.
ciao
  Pablo
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