[ptx] Brightness/colour correction in pano12 and nona

[Bruno Postle]

While I was looking around in adjust.c, there seems to be all the
code used by PTStitcher to do brightness/colour correction of image
pairs:

  void GetColCoeff ( Image *src, Image *buf, double ColCoeff[3][2] )
  void ColCorrect ( Image *im, double ColCoeff[3][2] )
  void DoColorCorrection ( Image *im1, Image *im2, int mode )

Could this be useful in nona?

-- 
Bruno