Re: Check for post-threshold binary image

Posted by Michael Doube on Apr 14, 2009; 2:50pm
URL: http://imagej.273.s1.nabble.com/Check-for-post-threshold-binary-image-tp3692956p3692958.html

Thanks everyone for your very quick responses.

Looks like I just have to use Gabriel's 'histogram method' and remember
to account for the signed<->unsigned byte issue.

Cheers

Mike

Michael Schmid wrote:

> Hi Mike,
>
> if your 8-bit images use ONLY pixel values of -1 and 0 they are  
> indistinguishable from binary images obtained by 'apply threshold'.
> (note that -1 is interpreted as 255 by ImageJ: it treats the image as  
> unsigned bytes).
>
> If you have also other pixel values, Gabriel's histogram-based method  
> will work (the same code is in ij.plugin.filter.Binary).
>
> Michael
> ________________________________________________________________
>
> On 14 Apr 2009, at 16:13, Michael Doube wrote:
>
>> Hi all,
>>
>> I'm looking for a short bit of Java that will check to see if an  
>> image is binary (result of Adjust->Threshold->Apply) or not. Just  
>> checking bit depth and making sure that pixel values are 0 or 255  
>> is not quite enough because
>>
>> ImageStack.getPixels(int n);
>>
>> returns an array of 0 (background) and -1 (foreground) elements,  
>> and I use raw 0 and -1 values in my logic.
>>
>> Cheers
>>
>> Mike

--
Dr Michael Doube  BPhil BVSc PhD MRCVS
Research Associate
Department of Bioengineering
Imperial College London
South Kensington Campus
London  SW7 2AZ
United Kingdom