Mikolaj Machowski on wrote...
| Hello,
|
| How to simulate Curves tool from GUI programs?
|
| I suppose there is some smart meddling with fx option but I would be
| grateful for any hints.
|
Yes and with the help of an external script (which uses gnuplot
underneath),
http://www.imagemagick.org/Usage/scripts/im_fx_curves
or a perl version (using Math::Polynomial library module)
http://www.imagemagick.org/Usage/scripts/im_fx_curves.pl
it is very easy to convert a set of curve 'points' into a mathematical
expression for the -fx function to use.
See IM Examples, Color Modifications,
Histogram 'Curves' Adjustments
http://www.imagemagick.org/Usage/color/#curves
A practical example is at
IM Examples, Advanced, "Aqua" Effects
http://www.imagemagick.org/Usage/advanced/#aqua_effects
For a speed up technue using a Color Lookup Table
http://www.imagemagick.org/Usage/color/#fx_to_lut
| Specifically I am interested in effects like described here:
|
| http://www.outbackphoto.com/workflow/wf_81/essay.html
|
That is not a 'curve' but a linear change. Though not a typical one as
you are doing a contrast change rather than a color limit change.
However given the two points the curves technique will still give you
the linear equation for the adjustment.
At this time there is no IM contrast option with specific arguments to
control the contrast adjustment. There are some automatic ones simular
to normalize, but no non-normalizing linear contrasting functions.
The closest would be a curved contrast adjustment known as
-sigmodial-contrast.
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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Very sad life. Probably a very sad death. At least there is symmetry!
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Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/
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