http://imagej.273.s1.nabble.com/Integrated-Density-and-Image-Scale-tp3696720p3696724.html
Err... thanks, I already knew that. My question is : what is the meaning of
> ID (and the area) is measured in pixels or in microns squared. Two
> different numbers.
>
> Peter
>
>
>
> -----Original Message-----
> From: ImageJ Interest Group [mailto:
[hidden email]] On Behalf Of
> Christophe Leterrier
> Sent: Monday, March 31, 2008 12:03 PM
> To:
[hidden email]
> Subject: Re: Integrated Density and Image Scale
>
> I'm not sure I understand.
> If the ID is about "samples" (what are samples ?) and not pixels, and the
> number of samples is the same in a scaled and unscaled image, then why is
> the ID output by ImageJ different for the same image before and after
> scaling ?
>
> christophe
>
> On Mon, Mar 31, 2008 at 5:57 PM, Gabriel Landini <
[hidden email]>
> wrote:
>
> > On Monday 31 March 2008 16:16:18 Christophe Leterrier wrote:
> > > I have a question about the "Integrated Density" measurement. In the
> > ImageJ
> > > docs it is stated:
> > > *"Integrated Density* - The sum of the values of the pixels in the
> image
> > or
> > > selection. This is equavalent to the product of *Area* and *Mean Gray
> > > Value* ."
> > > This is fine for unscaled images, where the area is expressed in
> pixels.
> >
> > > But what about scaled images ?
> >
> > The ID is about samples, not area. The number of samples in a scaled
> image
> > is
> > the same than in a non-scaled image.
> >
> > The integrated density is calculated as the sum of all the sample
> values.
> >
> > This happens to be the same as area*mean density because the mean
> density
> > is
> > calculated as the sum of all the samples divided the number of samples.
> > But
> > to calculate the mean density you have first to compute the integrated
> > density anyway, so you know this value.
> >
> > G.
> >
>