Thanks, this is marvelous as it is. I already used quite some times and it always gives excellent results. As an idea for future features I'd propose:
1) support predefined window size or -geometry option (linux)
./crtview -geometry 1200x800+100+100
it'd be good to take series of images
2) support to change brightness, saturation.
But both of these can be done post editing so not even that necessary.