Excluding black (255) from an image

Posted by elambeth on Aug 11, 2008; 5:59pm
URL: http://imagej.273.s1.nabble.com/Excluding-black-255-from-an-image-tp3695418.html

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?

Emily Lambeth, Graduate Student
Department of Biological Sciences
Notre Dame University