Hello,
You are right, there is a mistake in this functor. From looking at the
code and the reference paper (here
<http://www.lmars.whu.edu.cn/prof_web/zhangliangpei/rs/publication/Classification%20and%20Extraction%20of%20Spatial%20Features%20in.pdf>),
the *m_Alpha* parameter is supposed to be the constant applied to the
weighted mean. The parameter *m_DirectionStep* should be used instead.
I have also noticed something that bothers me : in
otbSFSTexturesFunctor.h, line 134, the distance of the segment is
computed between the _centre_ and the _last offset _in a particular
direction. I don't see why the centre is be used here. I would rather
use the _last offset in the opposite direction_. Otherwise, the length
and width measures are meaningless.
Here is the approach I propose :
- let choose a set of 5 directions.
- the last offsets will be computed for a set of 5*2 angles, giving an
angle step of : CONST_PI / 5 (as proposed by Julien Radoux)
- the distance should be computed between the last offsets measured at
two ends of the same direction
I have filled a bug report (http://bugs.orfeo-toolbox.org/view.php?id=955)
Any opinions on this ?
Best Regards,
Guillaume
Le 08/07/2014 16:47, Julien Radoux a écrit :
Hello,
I think that there is something wrong with otbSFSTexturesFunctor.h,
but maybe I did not understand something. Shouldn't the angle be
distributed between 0 and 2*PI instead of using the m_Alpha parameter?
Can anyone double check ?
//angle = m_Alpha * static_cast<double>(d);
angle = CONST_PI * static_cast<double>(d) / m_NumberOfDirections;
Thanks,
Julien
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