Re: Moment of inertia calculations

Posted by Mariam de la Iglesia on Feb 23, 2006; 7:48am
URL: http://imagej.273.s1.nabble.com/Moment-of-inertia-calculations-tp3703568p3703576.html

MOMENTOS DE INERCIA


----- Original Message -----
From: "Robert Dougherty" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, February 23, 2006 1:48 AM
Subject: Re: Moment of inertia calculations


> This macro might be a start.  It uses the center of mass as the axis of
> rotation, assumed perpendicular to the image.  (The conversion for a
> different axis appears to be to add Md^2 according to the "parallel axis
> theorem for moments of inertia," where M is the total mass and d is the
> displacement to the new axis.)  The macro presumably needs to be
calibrated

> to convert pixels into length units and image levels into mass.
>
> Bob
>
> Robert P. Dougherty, Ph.D.
> President, OptiNav, Inc.
> Phone [phone]
> Fax [phone]
> www.optinav.com
>
>
> // Find the center of mass
>
>      getBoundingRect(x1, y1, width, height);
>      xSum = 0;
>      ySum = 0;
>      sum = 0;
>      x2 = x1 + width;
>      y2 = y1 + height;
>      for (x=x1; x<x2; x++) {
>         for (y=y1; y<y2; y++) {
>             v = getPixel(x, y);
>            xSum += v*x;
>             ySum += v*y;
>             sum += v;
>           }
>      }
>      x0 = xSum/sum;
>      y0 = ySum/sum;
>
> // Find the moment of inertia about the center of mass
>
>      moment = 0;
>      for (x=x1; x<x2; x++) {
>          for (y=y1; y<y2; y++) {
>              v = getPixel(x, y);
>              rSq = (x-x0)*(x-x0) + (y-y0)*(y-y0);
>              moment = moment + v*rSq;
>          }
>      }
>      print(x0+" "+y0+" "+moment);
>
>
>
>
> > -----Original Message-----
> > From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of
> > Debra K Schneider
> > Sent: Wednesday, February 22, 2006 8:18 AM
> > To: [hidden email]
> > Subject: Moment of inertia calculations
> >
> > Hi
> > I am interested in measuring the moment of inertia of a bone slice.
> > Can this be done in ImageJ?
> > Thank you
> > Debby Schneider
>