Re: Pixel count via RGB range

Posted by Gus on Sep 10, 2010; 4:14pm
URL: http://imagej.273.s1.nabble.com/Pixel-count-via-RGB-range-tp3686979p3686981.html

Thanks Michael, that worked great. I'd love to automate this process but I
imagine that would be difficult because the user has to select the pixel?

Is there any way to build an attribute table for the image? I've done this
with a licensed GIS software but I'd rather use something that is open
source.


On Fri, Sep 10, 2010 at 4:05 AM, Michael Schmid <[hidden email]>wrote:

> 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!
>>
>