Re: negative centroid values

Posted by Wayne Rasband on Jul 19, 2006; 8:50pm
URL: http://imagej.273.s1.nabble.com/negative-centroid-values-tp3702087p3702088.html

Search the release notes for "centroid" and you will find this:

   v1.37g, 15 May 2006
       Fixed a bug that could cause calculated centroid
       coordinates to be incorrect with large images.

-wayne

On Jul 19, 2006, at 3:02 PM, Gwen Barnes wrote:

> Hi folks,
>
> I'm trying to find the centroid of a circular object, but I sometimes
> get
> negative (!) values for X or Y.
>
> I outline it with the polygon tool, under "set measurements" I chose
> area,
> centroid, and feret's diameter, and then I select "analyze, measure."  
> Most
> of the time this works fine.  However, if I encompass too large an
> area, I
> get negative values for either X or Y of the centroid.  My image is a
> 41 M
> tiff, 2552 pixels wide by 4200 pixels high.  My latest results from
> "measure" were:
>
> area: 1210035
> X:    1357.474
> Y:    -1649.551
> diam:    1343.317
>
> Whereas the actual values should be about:
>
> X:  1344
> Y:  1944
> diam: 1308
>
> In this case, maybe the Y value is the only incorrect one, but since
> there's
> no way the answer could be negative, it makes me distrust all the
> values.
>
> Is anyone else familiar with this problem, and does anyone have
> suggestions
> for getting the right answer?  Thanks.
>
> -Gwen
>
> --
> 01000111011101110110010101101110
> 010000100110000101110010011011100110010101110011
>