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

[Pablo d'Angelo]

On Thu, 01 Jan 2004, Ed Wildgoose wrote:

> >maybe for 8mm full circular lens, if we remap it to equirectangular
> >format, constructing the spherical panorama becomes a pure translation
> >problem.You can see this process from: 
> >http://www.path.unimelb.edu.au/~bernardk/tutorials/360/background/process.html
> >Thus phase correlation and klt can be used. Other wide angle
> >images also need to be remapped before correlation search.
> >
> You would also perhaps have problems with handheld shots if the rotation 
> was more than a few degrees off center.  I have seen a few papers on 
> rotational invariance, I wonder if you can make phase correlation 
> rotation invariant..?  I suspect not?

The Fourier mellin transform for example.
Or one could correlate polar images.

> Sorry for being ignorant, but why not?  Would you not simply remap all 
> the images assuming some fixed overlap top/bottom and then phase 
> correlate, then switch top and bottom, remap appropriately and re-run 
> the phase correlation - pick the best answer?

hmm, have to think about that. probably doable for a limited amout of
images.

> To be honest, if it was only the initial overlap which was the problem 
> then I suspect that most users would be ecstatic if they merely had to 
> visually drag the pictures into rough alignment and let the auto 
> algorithm do the rest!  PTGui has a nice mode which lets you do this (as 
> an example of an implementation).

Well, there is one big problem: I won't have time to implement a lot of
stuff in the next few weeks...

> Pablo, how accurate does the inial alignment have to be for your 
> optimisation approach to work?  How good is it at rejecting invalid 
> matches?  For example is a very simple algorithm which merely assumes a 
> 30 percent overlap on each picture, uses no phase correlation and just 
> tries all permutations of images until something matches, going to work?

Hmm, I don't think this will be very reliable, and consume a lot of time.
There definatly should be an estimate step. some of my pano's are not
accepted by autopano, because I shoot handheld, an the overlap size varies a
lot.

has anyone tried the current autopano program?

ciao
  Pablo
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