Feret measurements

[Rodrigo Gonçalves-4]

Hi guys,

I found that the definition of the Feret's measurements might change for different software/webpages.

To test how ImageJ goes with this, I opened a new image in Fiji under Windows, created a 'perfect' circle pressing CTRL to keep the ratio aspect, and then filled it and measured it.

The max and min Feret's look ok, but then I have FeretX and FeretY which I don't fully understand.

From the ImageJ user guide (http://rsbweb.nih.gov/ij/docs/user-guide.pdf and http://rsbweb.nih.gov/ij/docs/guide/146-30.html) I would expect to obtain the length of the object’s projection in the X (FeretX) and Y (FeretY) direction. If this is correct, then in a perfect circle MaxFeret, MinFeret, FeretX, FeretY should all have the same value, right? Because I expect the projection of a circle on the X axis will equal de circle's diameter, is that so?

But I get a Feret's diameter = 288 while FeretX and FeretY are 78 and 73, respectively.

What am I missing here?

________________________

Rodrigo J. Gonçalves

________________________

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[Rasband, Wayne (NIH/NIMH) [E]]

On Sep 27, 2012, at 3:59 PM, Rodrigo Gonçalves wrote:

> Hi guys,
>
> I found that the definition of the Feret's measurements might change for different software/webpages.
>
> To test how ImageJ goes with this, I opened a new image in Fiji under Windows, created a 'perfect' circle pressing CTRL to keep the ratio aspect, and then filled it and measured it.
>
> The max and min Feret's look ok, but then I have FeretX and FeretY which I don't fully understand.
>
> From the ImageJ user guide (http://rsbweb.nih.gov/ij/docs/user-guide.pdf and http://rsbweb.nih.gov/ij/docs/guide/146-30.html) I would expect to obtain the length of the object’s projection in the X (FeretX) and Y (FeretY) direction. If this is correct, then in a perfect circle MaxFeret, MinFeret, FeretX, FeretY should all have the same value, right? Because I expect the projection of a circle on the X axis will equal de circle's diameter, is that so?
>
> But I get a Feret's diameter = 288 while FeretX and FeretY are 78 and 73, respectively.
>
> What am I missing here?

... [show rest of quote]

FeretX and FeretY are the starting coordinates of the Feret diameter. Here is a macro that draws the Feret diameter.

   List.setMeasurements;
   x1 = List.getValue("FeretX");
   y1 = List.getValue("FeretY");
   length = List.getValue("Feret");
   degrees = List.getValue("FeretAngle");
   if (degrees>90)
       degrees += 180;
   angle = degrees*PI/180;
   x2 = x1 + cos(angle)*length;
   y2 = y1 - sin(angle)*length;
   setColor("red");
   Overlay.drawLine(x1, y1, x2, y2);
   Overlay.show();

-wayne

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[vitmat]

Hello,

a very beginner with Image J, I measured the longest diameter of two nanoparticles manually, without using the Analyze function. I set the scale, used the Straight Line tool to measure the diameter and then pressed the "M" key to store the diameter value in the Results list. I exported the results into an Excel file and found there is not only FERET but also a LENGTH column. The values differ slightly. Which are the true ones?

[Glen MacDonald-2]

under the Help menu, select 'Documentation and open the ImageJ User Guide to obtain a searchable web document. The left pane of the Guide indexes by menu and command.
You will want the section for Set Measurements - http://imagej.nih.gov/ij/docs/guide/146-30.html#toc-Subsection-30.7

Glen MacDonald
        Core for Communication Research
Virginia Merrill Bloedel Hearing Research Center
        Cellular Morphology Core
Center on Human Development and Disability
Box 357923
University of Washington
Seattle, WA 98195-7923  USA
[phone]
[hidden email]
[hidden email]





On Dec 20, 2012, at 10:54 AM, vitmat <[hidden email]> wrote:

> Hello,
>
> a very beginner with Image J, I measured the longest diameter of two
> nanoparticles manually, without using the Analyze function. I set the scale,
> used the Straight Line tool to measure the diameter and then pressed the "M"
> key to store the diameter value in the Results list. I exported the results
> into an Excel file and found there is not only FERET but also a LENGTH
> column. The values differ slightly. Which are the true ones?
>
>
>
>
> -----
> Vit Matuska
> --
> View this message in context: http://imagej.1557.n6.nabble.com/Feret-measurements-tp5000233p5001236.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

... [show rest of quote]

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[vitmat]

Dear Glen,
many thanks for your answer. I went through the manual before, but it didn't answer my question.
Let me put the problem in a different way. Let's focus purely on a diameter of a particle. If I want to measure Feret (manually), I'm expecting to obtain a "Feret" column filled with values in the output. The "Length" column is confusing me. There's no "Length" item in the Set Measurements menu. What does the "Length" mean? Is it the length of the line I made manually or is it a length of something else? Is Feret refined / recalculated length based on the length set manually by me? And thus, is Feret more accurate?
Cheers,

[Glen MacDonald-2]

Dear Vit,
Length is automatically selected when you choose a line tool.   pressing 'M' seems to be equivalent to the control-m or command-m for the Measure command.  (That is a new behavior to me.  but I never had any reason to stray from the old command-m.)  You could also threshold and select your particles with the magic wand tool or use Analyze Particles, which might be more efficient than drawing lines, provide Feret and MinFeret, but no straight line length.

Glen MacDonald
        Core for Communication Research
Virginia Merrill Bloedel Hearing Research Center
        Cellular Morphology Core
Center on Human Development and Disability
Box 357923
University of Washington
Seattle, WA 98195-7923  USA
[phone]
[hidden email]
[hidden email]





On Dec 20, 2012, at 1:03 PM, vitmat <[hidden email]> wrote:

> Dear Glen,
> many thanks for your answer. I went through the manual before, but it didn't
> answer my question.
> Let me put the problem in a different way. Let's focus purely on a diameter
> of a particle. If I want to measure Feret (manually), I'm expecting to
> obtain a "Feret" column filled with values in the output. The "Length"
> column is confusing me. There's no "Length" item in the Set Measurements
> menu. What does the "Length" mean? Is it the length of the line I made
> manually or is it a length of something else? Is Feret refined /
> recalculated length based on the length set manually by me? And thus, is
> Feret more accurate?
> Cheers,
>
>
>
> -----
> Vit Matuska
> --
> View this message in context: http://imagej.1557.n6.nabble.com/Feret-measurements-tp5000233p5001240.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

... [show rest of quote]

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