profile along line versus along rectangle

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

profile along line versus along rectangle

Batishko, Charles R
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
Reply | Threaded
Open this post in threaded view
|

Re: profile along line versus along rectangle

Wayne Rasband
ImageJ 1.37q will have a new "Interpolate Line Profiles" option in the
Edit>Options>Profile Plot Options dialog box. Un-check this option and
line profile plots will not be interpolated.

-wayne


On Aug 28, 2006, at 6:49 PM, Batishko, Charles R wrote:

> 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
>