Problems calculating 'proportion green' from pictures

Posted by sarah Al-beidh on
URL: http://imagej.273.s1.nabble.com/Problems-calculating-proportion-green-from-pictures-tp3686725.html

Hello all,

I am new to the list and to Image J and would be really grateful if one of you could offer some advice / assistance.
For a few months now, I have been trying to work out how to measure the vegetation cover from aerial photographs of 3m x3m plots (see attached photo for example). What I would like is a means of estimating the proportion of vegetation in each of my photographs wihtout having to draw lines around each green patch.
I have located a pdf on the Image J website describing how to determine the photosynthetic portion of a variegated leaf; however, this method (involving converting the image to greyscale and then binary) does not work for my photographs as the background here (bare soil) is not white and therefore this is not excluded when converting the image to black and white.
If anyone can give me a bit of help / direction regarding 1) whether this is possible with Image J and 2) how I could go about doing this with my photos, it would be greatly appreciated.

Many thanks in advance,
Sarah