Colour Area percentage

Posted by Satanic Mechanic on Sep 26, 2010; 7:02am
URL: http://imagej.273.s1.nabble.com/Colour-Area-percentage-tp3686784.html

Ok folks I once again must come to you again for advice and guidance. I have been through the searchs and can't quite see anything that is exactly what I am after but feel free to correct me on that. So here is the problem:

1. I have to work out the percentage areas of a certain colour randomly spread in patches over a photograph in this case usually brown - so far so good

2. So what I would like to do is this

a) Point to an example of the colour on the photograph and for other instances of this colour to be highlighted on the photo.
b) I then want to to adjust the 'range' of this colour (apologies for terminology) to include darker and lighter variations again for this to be highlighted on the photo

The above is similar in many ways to the 'Select by Colour' tool in Gimp

c) when I am happy with the 'range' - the area I have highlighted to be shown as a percentage.

I imagine this is not an uncommon process, but I just can seem to nail it or find the correct plug in.