Multi ROI freehand drawing and measure problem

[giorgio-2-2]

Dear all,
I'm trying to measure several hundreds of ROIs added to the ROI manager.

I've drawn them manually with the freehand selection tool. They represent
irregularly shaped objects (round-like or ellipse-like).
I guess that there's some special care that the program needs you to take in
drawing. The progam has no problem in measuring hundreds of ROIs with the
particles analyze tool, but there are probably some of mine which make the
program stop with the message "measuring..." under the buttons, with a blank
result window open. I then guess that I might have drawn some of them in a
way that ImageJ doesn't like.

Since I've to process several images drawing several hundreds of ROI
manually, before going on I need to know how to properly draw to have no
problems in measuring saved ROIs.

Do you know which could be my error in drawning?
Do you know about some special thing that I should do or not do in drawing
in order to avoid that ImageJ blocks?

I thank you very much in advance!
Giorgio

[Michael Schmid]

Hi Giorgio,

after a few tries I could reproduce the problem with the freehand tool.
With high magnification, I was drawing an L shape forward and  
backward, resulting in an L-shaped line with zero area enclosed. It  
can also happen with more complex shapes as long as one goes back  
along the same line as forward with sufficient accuracy to get no  
area enclosed.

Doing a measurement on this, I got area=0 and mean=NaN (32-bit image).

It seems that the check for an empty selection only works when it is  
a straight line forward and backwards.

I did not see the program getting stuck with simple "Measure". With  
the ROI manager I gotImageJ hang as in your case when "Ferets  
Diameter" is among the list of measurements.

The following is the contents of a sample roi causing this problem  
(hexdump of the roi file; 84 = hex 54 bytes).

49 6F 75 74 00 D9 07 00 00 A7 00 CD 00 A8 00 CE
00 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 01 00 01 00 01 00 00 00 01 00 01 00 00
00 01 00 01

Michael
________________________________________________________________

On 9 Apr 2009, at 17:23, Giorgio wrote:

> Dear all,
> I'm trying to measure several hundreds of ROIs added to the ROI  
> manager.
>
> I've drawn them manually with the freehand selection tool. They  
> represent
> irregularly shaped objects (round-like or ellipse-like).
> I guess that there's some special care that the program needs you  
> to take in
> drawing. The progam has no problem in measuring hundreds of ROIs  
> with the
> particles analyze tool, but there are probably some of mine which  
> make the
> program stop with the message "measuring..." under the buttons,  
> with a blank
> result window open. I then guess that I might have drawn some of  
> them in a
> way that ImageJ doesn't like.
>
> Since I've to process several images drawing several hundreds of ROI
> manually, before going on I need to know how to properly draw to  
> have no
> problems in measuring saved ROIs.
>
> Do you know which could be my error in drawning?
> Do you know about some special thing that I should do or not do in  
> drawing
> in order to avoid that ImageJ blocks?
>
> I thank you very much in advance!
> Giorgio

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