There is a shortcut that does exactly that. I have the pattern lock enabled but if I rotate my phone and then "tap and hold" the lock screen the camera automatically opens. This is configured in Settings>Lock screen>Lock screen options>Under Features>Camera quick access
Can you really do that??!! If so, HUUUUUGE security flaw!!! Pattern Lock/Pin Lock/Whatever Lock should NOT be bypassed by anything BUT the appropriate code or password... that's the whole point of it! If you can bypass that with a camera shortuct, then that gives anyone access to your phone (just open the camera, press the Home button and you're good to go).
EDIT: OK, panic aside, I just confirmed this is NOT possible in my phone (4.1.2 with Exynos patch). The option to even enable the gesture camera shortcut is not available when using Pattern Lock, PIN Lock, Face/FaceVoice Lock, and Password Lock. The only way to get this shortcut to work is by enabling Swipe Lock, No Lock, or Motion Lock, which clearly state NO security if chosen. I can put my pitchfork down now...