Thresholding problems

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Thresholding problems

Ben Pound
Hi everybody.
I'm new to this list, and obviously a newbie at ImageJ.
In a project that I'm doing, I keep trying to threshold an image, but one side always gets darker and distorts the image- which ruins my results, because the only dark parts that I want to see are the lines. I was wondering if there was any way to stop this distortation.
I put the pictures that i was using up on my MSN Skydrive account. The web address is (without the quotes): "http://cid-5a91a7808a91e6d9.skydrive.live.com/browse.aspx/Public"
If anyone could figure this out, it would be great! thanks. If not, thanks anyway.
 
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Re: Thresholding problems

Michael Schmid
Hi Ben,

this looks like a typical case for Process>Subtract Background.

You need to set "Light Background".
"Sliding Paraboloid" will probably do a better job at the
corners; try with a radius between 100 and 1000.

The image will be very bright after background subtraction,
but that's only because the original does not have much contrast.

An alternative could be the "fit polynomial" plugin at
   http://imagejdocu.tudor.lu/imagej-documentation-wiki/plugins/ 
fit_polynomial
using low order; maybe 2 in x, 1 in y.

Michael
________________________________________________________________


On 11 Jun 2008, at 21:48, Ben Pound wrote:

> Hi everybody.
> I'm new to this list, and obviously a newbie at ImageJ.
> In a project that I'm doing, I keep trying to threshold an image,  
> but one side always gets darker and distorts the image- which ruins  
> my results, because the only dark parts that I want to see are the  
> lines. I was wondering if there was any way to stop this distortation.
> I put the pictures that i was using up on my MSN Skydrive account.  
> The web address is (without the quotes): "http://
> cid-5a91a7808a91e6d9.skydrive.live.com/browse.aspx/Public"
> If anyone could figure this out, it would be great! thanks. If not,  
> thanks anyway.