[ptx] output of the colour correction curves

[dmg]

hi everybody,

(for the panotools readers I found an answer to my question about .amp
files --select the little pencil icon in the Curves window--so
disregard my previous message asking about this).


I implemented today the ability (in PTblender) to output the colour
correction curves in a way that they can be used in Photoshop (or the
Gimp, I think), instead of modifying the output panorama files.

Option -c creates a smooth colour correction curve (.acv)
Option -m creates an arbitrary colour correction map  (.amp)

I would be very grateful if somebody tries them in either the gimp
and/or in Photoshop. To load the non-corrected tiff, add a curves
layer, load the curve (if you select the "spline" icon you can load an
.acv, if you select the "pencil" icon you can load an .amp). I am not
sure at this point which one is better, my feeling is that the smooth
should produce better results, particularly in 16 bit images.

*******Implementation details:

The correction curves in PTblender are doubles from 0 - 255.0, they
are rounded to integers (using round) before they are output to the
curves files (the curve files take integers from 0 to 255).

* For arbitrary maps:  each point in the correction curve is output.

* For smooth maps (splines): only 14 points are output, including
  first and last. The other 12 are output each at a distance of 20 in
  the x-axis, starting at 20.

******** Implications for users:


With this feature you can do colour correction in 16 bit images. It is
painful, but it will work. Just make sure that the colour correction
layer is applied to one layer at a time, by selecting the "Use
previous Layer to Create Clipping Mask" option when you create the new
curves layer.

********* Known bugs:

Only full colour correction works at this point (no brightness or
colour only). I am going to start working on that.


Happy panoraming!

dmg

--
Daniel M. German                  "You cannot have the success without 
   H. G. Hasler ->                 the failures."
http://turingmachine.org/
http://silvernegative.com/
dmg (at) uvic (dot) ca
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