Raphael Compagnon wrote: > This command should do what you expect: > > pcomb -e 'ro=li(1)*ri(2);go=li(1)*gi(2);bo=li(1)*bi(2)' mask.pic > picture.pic >result.pic Ah yes, and I can threshold my mask image like this: pcomb -e 'lo=if(li(1), 1, 0)' input.pic > mask.pic Cheers, Chris