[Numpy-discussion] binary thinning
verveer at embl-heidelberg.de
Thu Dec 16 10:43:03 EST 2004
Thanks for using the nd_image code. It is helpful to get some user
feedback. I think I did not tell you in my last email, but your last
questions actually allowed me to find a few minor bugs and fix them...
> First, to answer your question about changing the order in which
> structures are applied. It turns out it does matter. I tried rotating
> the structures clockwise and counter-clockwise, pre-rotating the
> structure before doing the four rotations, and I permutating the
> order, and in some of those cases the results are different, although
> usually only slightly different - a couple pixels here, a few there.
This seems reasonable to me, I would expect that the order matters.
> Second, no matter what I tried, I could not duplicate the picture in
> the webpage.
> Third, besides the test image (off the webpage) I also tested a
> skeleton function on few other images using several packages available
> to me, including an old Matrox MIL, ImageJ, and Matlab. Each one of
> them produced different results. I'm not sure that one is more correct
> than another, they're probably all correct. In general the nd_image
> skeleton produces results similar to Matlab.
It seems then that there is no accepted single solution for the
skeleton, so I guess the code from nd_image is okay then.
> Peter, would you be interested in adding a few binary morphology
> functions to nd_image? So far I have working versions of borderkill,
> borderkeep, reconstruct, thinning, thickening, skeleton, skiz, and
> convex hull. Even though they were all produced with just what's there
> right now (erosion, dilation, and hit-or-miss) and a few numarray
> functions, it took a long time to figure out and could be helpful to
> the next guy. I'd be happy to send you what I got and/or post it.
One issue is that nd_image functions are supposed to be generic and
work in any dimension. So I kept the binary morphology low-level on
purpose, so far. But on the other hand, I don't see why we could not
add some stuff even if it only works in 2D (which I assume is the case
with your code.) Why don't you send me what you have and I have a look
in the next weeks?
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