[Insight-users] How can I get the pixels' values in .PNG after OtsuTresholding?

[Zachary Pincus]

Hello,

You might want to check that the Otsu thresholder is getting reasonable  
inputs. So try saving the output of the dilation and closing to a  
separate file to make sure that that is what you want. (Remember that  
if you save unsigned short images to a file you'll need a viewer [such  
as ImageJ] that is savvy to them, otherwise all you'll see is black.)

Then, check that the Otsu thresholder is calculating a legitimate  
threshold for your input image. You'll want to check what the  
calculated threshold is with the GetThreshold() method (after calling  
Update() of course), and make sure that that number is reasonable for  
the input image you provided.

Finally, you will want to make sure that your "bleck pixel findong"  
code (simple as it may be) is correct. Try saving the output of the  
Otsu calculator to a file and looking at it in a simple image viewer to  
see if it looks at all thresholded.

If none of this clears up the situation, you could send a *minimal*  
example of code that produces the problem to the list and I'll try to  
look it over.


Zach Pincus

Department of Biochemistry and Program in Biomedical Informatics
Stanford University School of Medicine


On May 19, 2005, at 9:31 AM, <syssboxx-reg at yahoo.fr> wrote:

> Hello everybody
> I have a problem with accessing the pixels' values;
> I do the folowing:
> I read a PNG file,then I use  grayscale dilatation and
> closing,then i use the OtsuTresholding filter setting
> the paratemeters to 255(white background) and 0(black
> object).Then I want to loop over ther tresholded image
> for detect the contour exterior of the object it and
> save it to another file.For this purpose I'm looking
> for the first black pixel in the object.It's the
> problem.It can't find any black pixels in the image.I
> tried to use unsigned char and unsigned short for
> InputImageType but  i can get the pixels' values.
> I supose after OtsuTresholding I have to be 0 and 255
> values.How can I access to values in order to can use
> it for my purpose?
>
>
>
> 	
>
> 	
> 		
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