Selecting pixels above a threshold

[Lasse]

How do I 'select' areas within my image that is above a certain threshold?
I can do it when working with RGB (Image/Adjust/Threshold), but when I try doing it with 16-bit images, the 'selection' button is absent.

I hope you can help me.

[Nilwik Rachel (BW)]

Hi all,

I have the same question, actually... I have a method for it now, but don't know whether this is the best solution.

What I do now is:
1) manually select a ROI;
2) threshold the whole image - WITHOUT clicking the 'set' button, so that the area within thresholded grey values is marked, but the image is not changed into binary;
3) measure the characteristics (area and mean grey value, in my case) of the ROI, while making sure 'Limit to threshold' is checked within the Set Measurement menu. This way it measures only the marked part of the ROI.

So, if thresholding within a ROI would be possible, that would be very nice. Would this be possible?
What I would like to know as well, if anyone happens to have that information, is, whether it is possible to visualize the area within threshold limits with different colors for different ROIs... for presentation purposes, that is. Or, presenting the 'area within threshold' from different ROIs in overlays would be an option as well, if I can then give these areas a color of choice in the overlay.

As you can probably recognize from the way I described how I do these analyses, I don't have the faintest idea about how programming works, although I have made a tiny macro executing these commands for me - except for the manual tracing part that is. Any answers/solutions in very easy language are very much appreciated :)

Thanks in advance!
rachel



-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of Lasse
Sent: Tuesday, June 26, 2012 1:44 PM
To: [hidden email]
Subject: Selecting pixels above a threshold

How do I 'select' areas within my image that is above a certain threshold?
I can do it when working with RGB (Image/Adjust/Threshold), but when I try doing it with 16-bit images, the 'selection' button is absent.

I hope you can help me.

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[dscho]

Hi Lase,

On Tue, 26 Jun 2012, Lasse wrote:

> How do I 'select' areas within my image that is above a certain threshold?

By performing the following two steps in order:

1) Image>Adjust>Threshold...
2) Edit>Selection>Create Selection

Ciao,
Johannes

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