TODO

todo
    o show the overlapping zone between target and last addition ?

    o compute coincidence ratio ?
    o sort images by bad specularity / coincidence ?

    o better rendering of histograms

    o individual colors cut gain gamma ratios settings ?
  x o [done] export as a layered pic ?
    o read EXIF expositions / focal / values ?

  x o [done] aggregate several falloff reference files for better interpolation ?  
    o artificially white the falloff ref and apply local color drifts for sensors stains ?
    o automatically match falloff according to exif values ?

    o try to remove noise before computing starsmap ?
  ? o try to correct falloff before computing starsmap ?
  ? o try to remove noise/falloff before finetuning ?

    o remove gradient from ultrablurred pic

done
    o use the whole overlapping zone for fine tuning ? beware of
      side effects : nb overlaping pixel count and ponderation ?