Re: Excluding black (255) from an image

Posted by Theresa Swayne on Aug 11, 2008; 6:38pm
URL: http://imagej.273.s1.nabble.com/Excluding-black-255-from-an-image-tp3695418p3695419.html

Hi Emily,

If I understand the problem correctly, one way to solve it is:

-- (Image>Adjust>Threshold. Set upper threshold to 254. Lower  
threshold should be 0. Select "Over/Under" from the drop-down menu to  
see the excluded pixels in green.
-- Analyze > Set Measurements. Check "Mean" and "Limit to Threshold."
-- Analyze > Measure.

This will give you the mean of the pixels that are between 0 and 254,  
inclusive.

Hope this helps.
Theresa

On Aug 11, 2008, at 1:59 PM, elambeth wrote:

> I am working with red stained images of frog liver.  There are  
> pigment cells
> in the liver that are black, and should not count for the  
> quantification of
> the red stain.  I want to know the mean gray value of the red  
> pixels, and I
> know this is on the histogram, but I do not know how to exclude the  
> black
> pigment cells from the histogram (basically I want a histogram of  
> the red
> stain only).  Is there any way to exclude the black?
>

------------------------------------
Theresa C. Swayne, Ph.D.
Manager, Confocal and Specialized Microscopy Shared Resource
Herbert Irving Comprehensive Cancer Center, Columbia University
1130 St Nicholas Ave, 222A
New York, NY 10032

212-851-4613

[hidden email]
http://cancercenter.columbia.edu/confocal/