Threshold

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Threshold

Paul Stutzman
I am having difficulty creating binary images using the Threshold  
that is called from Image-Adjust.   I want to generate a binary where  
the feature of interest is gray 255 and the remainder is 0. I used  
the picker to set the gray value to 255 and use the scroll bars to  
set upper and lower bounds.  Interestingly, I still see low count  
noise even after the lower bound is set well above the noise gray  
levels.  Next, when attempting to create the binary, a window  
detailing options "Apply LUT' appears where I de-select the option  
for black foreground, white background.  The resulting window is a  
uniform level (62 in todays attempt) using the red option; using the  
black and white option in another attempt results in a uniformly gray  
image, again at level 62.  Another attempt using the Black-White  
option and picker set to 255 resulted in the entire image being set  
to 255.  I am using ImageJ 1.34S on a G5.


Paul Stutzman
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Re: Threshold

Wayne Rasband
> I am having difficulty creating binary images using the
> Threshold  that is called from Image-Adjust.   I want to
> generate a binary where  the feature of interest is gray 255
> and the remainder is 0. I used  the picker to set the gray
> value to 255 and use the scroll bars to  set upper and lower
> bounds.  Interestingly, I still see low count  noise even
> after the lower bound is set well above the noise gray 
> levels.  Next, when attempting to create the binary, a
> window  detailing options "Apply LUT' appears where I
> de-select the option  for black foreground, white
> background.  The resulting window is a  uniform level (62 in
> todays attempt) using the red option; using the  black and
> white option in another attempt results in a uniformly gray 
> image, again at level 62.  Another attempt using the
> Black-White  option and picker set to 255 resulted in the
> entire image being set  to 255.  I am using ImageJ 1.34S on
> a G5.

The easiest way to do this is to check "Black foreground, white
background" in the "Apply LUT" dialog and then press shift-i
(Edit>Invert).

-wayne