invert black and white values

Posted by Abi on Apr 28, 2013; 6:37am
URL: http://imagej.273.s1.nabble.com/invert-black-and-white-values-tp5002832.html

Hi,
I've only just downloaded image J and this is probably a really silly question, sorry!
I'm trying to set the threshold for an image, a black image on a white background.  I want the black values to have a count of 255 and the white of 0, but it's coming up the other way round.  When I use the computer at work it comes up the way I want it.
Can anyone tell me what I'm doing wrong please?
Thanks
A