An issue related to this came up once before, and since there were no
replies, it might be that no plugin exists for this. However, the
math is pretty simple:
With a center of x0, y0 and three points of x1,y1 etc:
a = [[x1,y1,1], [x2,y2,1], [x3,y3,1]]
d = -[[x1^2+y1^2, y1, 1], [x2^2+y2^2, y2, 1], [x3^2+y3^2, y3, 1]]
e = [[x1^2+y1^2, x1, 1], [x2^2+y2^2, x2, 1], [x3^2+y3^2, x3, 1]]
x0 = -d/(2*a)
y0 = -e/(2*a)
Jonathan
On 9/22/06, Henry Barwood <
[hidden email]> wrote:
> I need to locate the X,Y coordinates of the center of a circle or arc. Is
> there a macro or plugin that does this? Thanks.
>
> Henry Barwood
> Associate Professor of Science, Earth Sciences
> Department of Math and Physics
> MSCX 312G
> Troy University
> Troy, Alabama
>
[hidden email]
>
> -----Original Message-----
> From: ImageJ Interest Group [mailto:
[hidden email]] On Behalf Of Wayne
> Rasband
> Sent: Friday, September 22, 2006 12:08 PM
> To:
[hidden email]
> Subject: Re: Specify and position an ROI
>
> > When I use the specify tool to create a ROI, it appears to place the
> > center of the ROI on the specified X,Y coordinates. Is there a way
> > to place the left or right side (Maximum X or Minimum X coordinate)
> > of the ROI at a specific position? Thanks.
>
> Use the Edit>Selection>Specify command. It places the center of the
> selection at the specified coordinates if "Centered" is checked,
> otherwise it places places it at the upper left corner at the specified
> coordinates.
>
> -wayne
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