Re: Image subtraction, distance maps and skeletons to measure width

Posted by Gabriel Landini on May 14, 2011; 7:50am
URL: http://imagej.273.s1.nabble.com/Image-subtraction-distance-maps-and-skeletons-to-measure-width-tp3684590p3684591.html

On Friday 13 May 2011,  eburell wrote:

> I am trying to measure the thickness of a sponge spicule. I was told to
> dilate a binary image (from a HSB brightness slide) of the spicule and
> subtract the original to create a perimeter. In the next step, a distance
> map was to be created and I assume this can be done with the EDM plugin
> (I'm currently having problems with this plugin and I am unsure of what a
> proper output from using this would be). Finally, a skeleton of the
> spicule was to be created.
>
> I am however not sure on how to calculate the distance from the skeleton to
> the perimeter using the distance map. Could anyone be so kind as to offer
> me some tips on this step?

Better than that, binarise the spicules, duplicate the image and compute their
distance map in the duplicate.
The maximum grey value in each spicule (in the distance map image) corresponds  
to the thickness in pixel units (or rather the distance from that foreground
pixel to the closest boundary pixel in the object).
You can get the thickness of each spicule using the particle analyser on the
binary image and "redirecting" the measurements to the distance map image to
extract the "Maximum" grey value.

Cheers

Gabriel