[ptx] perspective correction

[Pablo d'Angelo]

Daniel M. German wrote:
>  Steve Schacht twisted the bytes to say:
> 
> This is already implemented in PTmender (currently in subversion, I
> don't think we have officially released it). There is a catch, though,
> it only works for TIFF or JPG inputs and _only_ when the output is
> TIFF. 

It is supported by hugin and nona since 0.5, and it works on my machine with
the example image Steve send me. I'm trying to figure out why it doesn't on
his machine.

ciao
  Pablo