Posted by
Michael Schmid on
Dec 30, 2007; 10:11am
URL: http://imagej.273.s1.nabble.com/need-help-on-various-watershed-segmentation-algorithms-tp3697689p3697690.html
Hi Gabriel,
for Process>Binary>Watershed the minimum waist size (diameter where
the particle can be cut by segmentation) is 1595 pixels.
Wider particles are not segmented. The length of the particle does
not matter.
This restriction comes from using the internal 16-bit EDM
(Euclidian Distance Map), which has has a scale factor of 41 for
a single pixel distance:
41*1596/2 = 32718 (the distance to one border is half the diameter)
This is almost 2^15 = 32767, the limit of (signed) 16-bit numbers.
---
Process>Binary>Find Maxima/Segmented Particles:
This is very different from skiz (skeleton of the [binary] background).
For segmentation, Find Maxima applies the watershed algorithm to
the *pixel values*, thus it needs a grayscale image as an input,
not a binary one. This algorithm works best if the particles become
denser towards the center; see the sample image for Segmented Particles
at
http://rsb.info.nih.gov/ij/docs/menus/process.html#binaryBest wishes,
Michael
_____________________________________________________________________
On Fri, 28 Dec 2007 22:08:20 +0000 Gabriel Landini
<
[hidden email]> wrote:
>On Friday 28 December 2007, Michael Schmid wrote:
>> to increase your confusion, there is at least one more:
>> Process>Binary>Find Maxima can do Watershed segmentation based
>> on *pixel values* (as the watershed command by Daniel Sage,
>> without preprocessing).
>
>Ah, yes, sorry I forgot that one, thanks.
>
>Is that the same as the skiz? (skeleton of the [binary] background)?
>
>I guess (but could be very wrong) that the Process>Binary>Watershed has a
>limitation of the maximum 255 computable distances same as the EDM command?
>
>Some time ago I wrote a macro to do EDMs beyond the 255 limit of built in EDM
>function (in the Morphology collection). That may come in handy if the
>particles are larger than 255 in diameter, but it will not do the subpixel
>correction that Michael mentioned.
>
>Regards,
>
>G.
>