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Science Forum Index » Image Processing Forum » question about dilation...
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 Posted: Thu Jun 05, 2008 2:59 am |
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Guest
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Hi everyone,
I am currently doing a threhold based segmentation (Otsu segmentation)
on an image and would like to connect some of the voxels using
dilation. What is the normal approach here? Usually, what kind of
structuring element would one use? is there a rule to determine this
or do you just try different ones till one of them seems to work?
Also, what about the subsequent erosion? What sort of structuring
element is recommended there?
Thanks,
Luca |
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| Frank Schmitt... |
| Posted: Thu Jun 05, 2008 9:27 am |
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Guest
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luca.pamparana at (no spam) gmail.com writes:
Quote: I am currently doing a threhold based segmentation (Otsu segmentation)
on an image and would like to connect some of the voxels using
dilation. What is the normal approach here? Usually, what kind of
structuring element would one use? is there a rule to determine this
or do you just try different ones till one of them seems to work?
Also, what about the subsequent erosion? What sort of structuring
element is recommended there?
You should use the same structuring elements for both. I'd use balls as
structuring element or cubes if speed matters more than efficiency.
--
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that a signature usually consists of up to four lines, this gives you enough
space to spread a tremendous amount of information with your messages. So seize
this opportunity and don't waste your signature with bullshit nobody will read. |
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| ImageAnalyst... |
| Posted: Thu Jun 05, 2008 12:44 pm |
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Guest
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On Jun 5, 8:59 am, luca.pampar... at (no spam) gmail.com wrote:
Quote: Hi everyone,
I am currently doing a threhold based segmentation (Otsu segmentation)
on an image and would like to connect some of the voxels using
dilation. What is the normal approach here? Usually, what kind of
structuring element would one use? is there a rule to determine this
or do you just try different ones till one of them seems to work?
Also, what about the subsequent erosion? What sort of structuring
element is recommended there?
Thanks,
Luca
----------------------------------------------------
Luca:
I usually do a closing (dilation followed by erosion) rather than a
dilation because I want to end up with the same size structures before
segmentation rather than larger structures. I use a round structuring
element because if I use a box or cube I get artifacts. If you use a
square structuring element on an image of a thin ring-shaped
structure, you'll see bogus artifacts at 45 degrees, 135 degrees,
etc. These are minimized with a circle. Try different window sizes
and on the original gray scale image or on the binarizy, thresholded
image and just see what works best in your situation.
Regards,
ImageAnalyst |
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| Science.Medical.Imaging List... |
| Posted: Sat Jun 07, 2008 6:18 am |
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Guest
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On Jun 5, 3:44 pm, ImageAnalyst <imageanal... at (no spam) mailinator.com> wrote:
Quote: On Jun 5, 8:59 am, luca.pampar... at (no spam) gmail.com wrote:
Hi everyone,
I am currently doing a threhold based segmentation (Otsu segmentation)
on an image and would like to connect some of the voxels using
dilation. What is the normal approach here? Usually, what kind of
structuring element would one use? is there a rule to determine this
or do you just try different ones till one of them seems to work?
Also, what about the subsequent erosion? What sort of structuring
element is recommended there?
Thanks,
Luca
----------------------------------------------------
Luca:
I usually do a closing (dilation followed by erosion) rather than a
dilation because I want to end up with the same size structures before
segmentation rather than larger structures. I use a round structuring
element because if I use a box or cube I get artifacts. If you use a
square structuring element on an image of a thin ring-shaped
structure, you'll see bogus artifacts at 45 degrees, 135 degrees,
etc. These are minimized with a circle. Try different window sizes
and on the original gray scale image or on the binarizy, thresholded
image and just see what works best in your situation.
Regards,
ImageAnalyst
As said already,
[1] The scale of the structuring element can be determined by the size
of the smallest opening you want to keep open after the 'closing'.
[2] The shape of the structuring element can be determined by the
shape of the smaller features in the image.
Prashant Chopra
Moderator,
Science.Medical.Imaging group
http://groups.google.com/group/medicalimagingscience |
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