Re: Connectivity used in "Analyze Particle ..." and "Wand (tracing) Tool"

Posted by karo03 on
URL: http://imagej.273.s1.nabble.com/Delaunay-update-tp3694375p3694379.html

Gabriel, thank you for the hint. Very helpful! I will see to prepare a  
macro Wand 2 to test the BinaryReconstruction4/8.

Michael, In fact I did not threshold the image! It is a result of the  
Delaunay/Voronoi plugin from Johannes (Dscho?) after some broohaha  
with foreground and background color switches!. However, ImageJ1.42c  
(daily build) selects particels in the described way! I think I should  
preserve that example for tests!

Meanwhile I see and remind me to earlier findings that wand selects  
the next object to the right even if the selection point is not inside  
the object. This is perhaps an explaination for the queer selection on  
the right side!

Thanks again for the quick answers

Karsten

Am 27.11.2008 um 18:11 schrieb Gabriel Landini:

> On Thursday 27 November 2008 16:57:39 Karsten Rodenacker wrote:
>> Hi, Image analysis and -J experts,
>>
>> I have an example were I don't fully understand the routines "Analyze
>> Particle ..." and "Wand (tracing) Tool"!
>>
>> The image http://picasaweb.google.com/lh/photo/8Yo_5vJ1zLKZGwP22oDgsw
>> delivers under "Analyze Particle ..." three particles (white is
>> foreground). That is understandable, seemingly eight-connected
>> neighborhood (of foreground) is assumed. Possibly four-connectedness
>> could be helpful in such cases with thin lines dividing the  
>> particles.
>
> I think that your image has 4-conn particles. If you run Particles4  
> plugin with the label option you will get 20 particles.
> If you created this with a watershed/skeletonisation, then to make  
> it easier, you could use a 4-conneected watershed (which should give  
> 8-connected particles).
>
> If you analyse the image with the Particles8 plugin you get only 3  
> particles.
>
>> But now, trying to overcome this problem by selecting the particles
>> with "Wand (tracing) Tool", possibly in a macro, I run into
>> difficulties. Clicking into particles on the left side of the image
>> selection is okay, Wand is using 4-connectedness! Clicking into one  
>> of
>> the two right-most particles seemingly wand is selecting background!
>>
>> Is there any way to select one of these two right-most particles?
>
> That is a job for the BinaryReconstruct4 plugin in the Morphology  
> collection. Now this is not compiled into a class, because I have  
> not had time to test it thoroughly. If you test it, please send me  
> some feedback.
>
> You could get the XStart YStart points with Particles4, then create  
> a new image with those pixels set for the particles you want to  
> select and BinaryReconstruct4 with the original as mask and the new  
> image as seed.
>
> I hope it helps.
>
> Gabriel