Background Subtraction Method

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Background Subtraction Method

Post  Alison on Wed May 21, 2008 3:51 am

We are getting an error (greater than 25% of pixels are black) when attempting to use the background subtraction method. There are lots of black spots, especially to the left side of the scan, and more than 500 particles are identified even when doing a scan with nothing on the screen. We are using the natural image process method and the none color balance. Any suggestions on how to fix this problem would be appreciated.
Thanks,
Alison

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Background subtraction method

Post  picheral on Wed May 21, 2008 12:34 pm

Dear Alison,

I just posted the new Zooprocess 5.05 onto the website. This versions keeps the same 25% limit for the B/W ratio. I assume that this limit is a real maximum that should not be overpassed. You can anyhow press YES and go on processing but it would be a problem in batch mode.
I would like to check your images before allowing you to change the 25% setting.
I will send you an email to give you a private FTP addresse to post the image that makes problem.

Be aware that this new value will be applied to all projects.... and do not forget to change it when you will download new release.

Regards
Marc P.

To change manually the 25 % limit in Zooprocess :
Start ImageJ,
Edit (go to the macros folder)
Select "Zooscan_Particle_Analysis.txt" macro and open it
Search for "bwratio" (CTRL F).
Change "bwratio = 25"; to "bwratio = 40"; or a greater value.
Save macro (CTRL S).

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Background subtraction method (2nd) / Threshold

Post  picheral on Wed May 21, 2008 12:38 pm

Dear Alison,
The problem should not be the 25% limit that is a good security again.
You have probably changed the image process method to "neutral" without changing the threshold value. The normal threshold for the "neutral" processed images is typically 243 (not 250 !) and can sometimes be set up to 247.
Can you edit the configuration file and check ?
Regards
Marc P.

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Re: Background Subtraction Method

Post  aspear on Fri May 15, 2009 7:25 pm

Alison wrote:We are getting an error (greater than 25% of pixels are black) when attempting to use the background subtraction method. There are lots of black spots, especially to the left side of the scan, and more than 500 particles are identified even when doing a scan with nothing on the screen. We are using the natural image process method and the none color balance. Any suggestions on how to fix this problem would be appreciated.
Thanks,
Alison

I am currently having the same issue. Please advise. My threshold is at 243 I think
Thanks,
Adam

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Re: Background Subtraction Method

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