The Screen shot plugin enabled from Compiz Config Settings Manager doesn't work properly. The screen shots of the selected areas get overshadowed with blue color..
Not as clear of a screen shot as I would get in previous Ubuntu versions.
This is a known bug in Compiz: https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/771875
I'm sorry you are getting this problem, but as tshirtman points out, it is a known bug. What you should probably do is install shutter or lookit and use them for taking screenshots.
In both applications you can even use the same (or at least a similar) shortcut.
P.S. I will add further instructions later.
Alternatively you can use the
Take Screenshot tool, which is installed by default. When you run this from the dash you can choose the option to capture a selected area.
Shortcuts are Print for the whole screen and Alt+Print for the active window.
You can select an area to capture directly with the command
gnome-screenshot -a after pressing Alt+F2. You could create a shortcut for this (i. e. Ctrl+Print), but as I try this here it doesn't seem to work fluently - sometimes I have to press for a second or two. (Problem described here)
In Ubuntu 12.04 Precise the
Screenshot section in
System Settings →
Shortcuts became enhanced. Press Shift+Print to take a screenshot of a selected area. This works without any problems.
Unity is the reason for me. When I disable Unity Panel or when I switch to Ubuntu Classic, the screenshot by +Button1 works superb.
The Ubuntu Unity Plugin is a real problem that serves to make a blue overlay on screen shots. It has some kind of conflict with Screenshot feature.
Also I feel that Avant Window Navigator (AWN) is real good replacement for Unity. Now I can take screenshots with Inbuilt compiz feature.