[ptx] Projections (was Alternative fisheye projections)

[Bruno Postle]

On Fri 07-Apr-2006 at 01:53 +1000, Peter Gawthrop wrote:

> So far, I have modified sphere-slicer.pl by Bruno Postle to do this
> for Mercator's projection (using formulae from
> http://mathworld.wolfram.com/topics/MapProjections.html). The problem
> is that it is slow. Before I plunge in to other projections, I would
> like to be sure I am on the right path.

Perl is _really_ slow for this, the sphere-slicer approach will give 
you nice spline16 interpolation, but it takes forever because of the 
perlish dynamic typing of variables.

Alternatively you can take the same approach as fisheye2stereographic.

Although this is a perl script, none of the image transformation is 
done in perl which is why it is as fast as nona/PTStitcher (the 
Imager library doesn't do interpolation, so the script implements a 
linear interpolator itself).

> Do you thing perl is the correct approach? Or would modifying nona/hugin be
> a better approach? I guess the main issues for me are speed and
> interpolation quality.

Ultimately I would like to see Mercator and Stereographic in hugin 
and or libpano12, but I think you could get reasonable quality, 
quick and easy results by modifying the fisheye2stereographic 
script.

-- 
Bruno