Draw circle around point

[imagej-user]

Dear ImageJ Forum,

Despite intensive googleing and searching within this forum, I have not found a solution to my problem yet.
My task is to find find out the shortest distance between a point and an irregular surface. I wanted to do this as follows:
Draw a circle around the point (meaning the point is the middle point of the circle) and keep on drawing (hold left mouse button) as long as the circle hits the surface somewhere (release left mouse button).
Then measure the radius of the circle ("Analyze" -> "Measure"). The measured distance (radius) should be equal to the shortest distance between that point and the surface.

At first, I tried it with the built-in ellipse/circle tool in ImageJ but the problem is that ImageJ does not draw the circle from the middle point (concentrically) but from the top.

Then, I found the concentric circle macro on the internet. The problem with this tool is, that it only draws circles with pre-defined radii. This does not work for me, as the radius of the circle is the unkown variable I want to measure.

According to my understanding, the best solution would be a cicrle tool (like the built-in) which lets you draw a circle from the center.

I hope my problem is understandable. I would appreciate your help very much. Thank you!

[MODEL, MICHAEL]

You can use Distance Map (Process-Binary) based on the surface and see where your point lies.

Mike Model

-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of imagej-user
Sent: Wednesday, January 07, 2015 12:35 PM
To: [hidden email]
Subject: Draw circle around point

Dear ImageJ Forum,

Despite intensive googleing and searching within this forum, I have not found a solution to my problem yet.
My task is to find find out the shortest distance between a point and an irregular surface. I wanted to do this as follows:
Draw a circle around the point (meaning the point is the middle point of the
circle) and keep on drawing (hold left mouse button) as long as the circle hits the surface somewhere (release left mouse button).
Then measure the radius of the circle ("Analyze" -> "Measure"). The measured distance (radius) should be equal to the shortest distance between that point and the surface.

At first, I tried it with the built-in ellipse/circle tool in ImageJ but the problem is that ImageJ does not draw the circle from the middle point
(concentrically) but from the top.

Then, I found the concentric circle macro on the internet. The problem with this tool is, that it only draws circles with pre-defined radii. This does not work for me, as the radius of the circle is the unkown variable I want to measure.

According to my understanding, the best solution would be a cicrle tool (like the built-in) which lets you draw a circle from the center.

I hope my problem is understandable. I would appreciate your help very much.
Thank you!



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[Michael Schmid]

Hi anonymous user,

you can draw a circle centered at a point when pressing Command-Shift on a Mac (CTRL-Shift on Linux/Windows).


There is a more elegant way:

Calculate the Euclidian Distance Map (EDM) and just read the value from the status line of the ImageJ panel
  http://rsb.info.nih.gov/ij/docs/guide/146-29.html#toc-Subsubsection-29.8.10

You need a binary image as an input for the EDM (everything above the surface being black).  Have the cursor over the EDM, and use Synchronize Windows to see the position in the original image that corresponds to a given point in the EDM:

http://rsb.info.nih.gov/ij/docs/guide/146-30.html#toc-Subsubsection-30.14.8


Michael
________________________________________________________________
On Jan 7, 2015, at 18:34, imagej-user wrote:

> Dear ImageJ Forum,
>
> Despite intensive googleing and searching within this forum, I have not
> found a solution to my problem yet.
> My task is to find find out the shortest distance between a point and an
> irregular surface. I wanted to do this as follows:
> Draw a circle around the point (meaning the point is the middle point of the
> circle) and keep on drawing (hold left mouse button) as long as the circle
> hits the surface somewhere (release left mouse button).
> Then measure the radius of the circle ("Analyze" -> "Measure"). The measured
> distance (radius) should be equal to the shortest distance between that
> point and the surface.
>
> At first, I tried it with the built-in ellipse/circle tool in ImageJ but the
> problem is that ImageJ does not draw the circle from the middle point
> (concentrically) but from the top.
>
> Then, I found the concentric circle macro on the internet. The problem with
> this tool is, that it only draws circles with pre-defined radii. This does
> not work for me, as the radius of the circle is the unkown variable I want
> to measure.
>
> According to my understanding, the best solution would be a cicrle tool
> (like the built-in) which lets you draw a circle from the center.
>
> I hope my problem is understandable. I would appreciate your help very much.
> Thank you!

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