http://imagej.273.s1.nabble.com/Integrated-Density-and-Image-Scale-tp3696720p3696729.html
Rigo, I think you did not read my question... This is precisely about the
> You're correct, pixels are the elementary units. You need to calibrate
> your
> pixels to your scale. For example, if your scale (which is arbitrary) is
> 1
> micron. Then, how many pixels are equal to 1 micron. Basically, you
> understand the fundamental concept regarding ID. Now you you need to
> understand your imaging system.
>
> On Mon, Mar 31, 2008 at 10:27 AM, Christophe Leterrier <
>
[hidden email]> wrote:
>
> > Err... thanks, I already knew that. My question is : what is the meaning
> > of
> > the ID in case of a scaled image ? This is not "The sum of the values of
> > the
> > pixels in the image or selection" anymore, right ? And what intensity is
> > taken for each square micrometer to compute such a scaled ID ?
> >
> > On Mon, Mar 31, 2008 at 6:38 PM, Saveliev, Peter <
[hidden email]>
> > wrote:
> >
> > > 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.
> > > >
> > >
> >
>