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profile along line versus along rectangle

Posted by Batishko, Charles R on Aug 28, 2006; 11:49pm
URL: http://imagej.273.s1.nabble.com/profile-along-line-versus-along-rectangle-tp3701722.html

In trying to associate specific pixels in an image with other correlated
data, based on features along a profile, I've using the line selection
tool to draw a line in the image, then using the Analyze/Plot Profile
function. When I noticed that the feature I was interested in did not
appear to be correctly associated with the pixel I thought it was in the
image, I wondered if I might be misunderstanding something. A colleague
took a look at it and replied as follows

-------------------------
...if you plot a profile using the line selection tool, ImageJ uses some
kind of interpolation between image pixel values to create the y-values
in the profile plot.  However, if you use the rectangular selection tool
to select the [nth] row and plot the profile, the image data and the
profile data are consistent.  So give the rectangular selection tool a
try and see if that works.
-------------------------

I presume that if I use a rectangular selection tool and select other
than a 1-pixel wide area, there is an averaging across the width,
however, I want a line profile, not an average, so that drove me to use
the line selection tool.

Comments? Am I misunderstanding what goes on in using the line selection
tool then doing a profile? Is my colleague correct that I should be
using the rectangular selection tool? Or, am I making some other
mistake?

Thanks!
Chuck