Creating a Background ROI

Posted by Shiva A. Portonovo on May 17, 2006; 11:13pm
URL: http://imagej.273.s1.nabble.com/Creating-a-Background-ROI-tp3702732.html

For the purpose of measuring noise intensity in my image stacks, I'd like
to be able to measure the average intensity of the background in much the
same way that I do for individual ROIs.  Basically, I want to make one big
ROI out of anything that isn't already a specific ROI.  I've heard of
subtracting out the ROIs with a mask, but I don't want the holes to be
given an intensity value of 0 and averaged in with the background (thus
lowering the overall mean intensity accordingly)... in essence, I don't
even want the holes to be considered.

Is there a standard tool/plugin/macro that I can use for this.

Thanks so much for any assistance.