Re: Pixel count via RGB range

Posted by Michael Schmid on Sep 10, 2010; 8:05am
URL: http://imagej.273.s1.nabble.com/Pixel-count-via-RGB-range-tp3686979p3686980.html

Hi John,

one option might be the Versatile Wand

http://imagejdocu.tudor.lu/doku.php?
id=plugin:segmentation:versatile_wand:start

(the link should be one line).

Use Connectedness 'Non-Contiguous', Gradient Tolerance off (0),  
Include Holes off.

If you select the tool, click on a pixel with the typical color and  
then open the Versatile Wand Options (dobule click the tool icon).  
You can use preview and play with the tolerance and Color sliders to  
get the best result.
Then, Analyze>Measure will give you the area selected (make sure that  
'Area' is selected in Set Measurements).

Michael
________________________________________________________________

On 8 Sep 2010, at 23:46, John Carpenter wrote:

> Hello,
>
> I'd like to use this software for digital vegetation profiles. The  
> idea is
> to place a 0.5m x 0.5m white background (drop cloth, poster  
> board,etc.) in a
> field plot and take a picture of it from a certain distance. I'd  
> then crop
> out just the half meter square area to analyze.
>
> I suspect that the leaves and twigs would have a fairly small RGB  
> range, as
> compared to the white background, that I could specify and then  
> have ImageJ
> count the pixels in that range. All that's left is to divide by  
> that number
> by the total pixels to get a percent cover of vegetation.
>
> If someone could point me in the right direction on how to do this  
> with
> ImageJ I would be very grateful.
>
> Thanks!