Slightly related to this off topic post... http://webcam.selwyn.govt.nz
Is the webcam in the IT office at work.. Folks who have been on the list a while will remember it was online back in 2002 for a while as well, but at the other end of the office. I don't work in there anymore, I'm up the corridor, but you can watch some of the IT folks going about their daily toil.. Or at the moment you can just watch the empty room, and move the camera about, as it appears that someone has left the lights on! :-). (If it's a dark picture, someone has turned off the lights since I posted this! Oh, the relevance is that this uses a CLI php/libgd script to process the image.. Cheers, CHris H.. On Tue, 2006-10-10 at 13:51 +1200, Andrew Errington wrote: > Hi, > > Can anyone comment knowledgably on determining the light level in a JPG > image snapped by a webcam? > > I have the simple requirement of taking hourly snapshots from my webcam in > the back garden and posting them on my webpage. At the moment I have a > cron job, which I tweak during the year to adjust when it takes a picture > (i.e from 8 to 5 in winter to 5 till 10 in summer), but really it should be > automated. I could rig up a light sensor, and the PC could query it before > taking a webcam image, but really, the webcam itself is a light sensor > (duh!). > > I am thinking of the imagemagick 'identify' command, and maybe extracting > the mean value of the red, green and blue channels and comparing them to a > hard limit. Does this idea have merit, or is there a better tool? > > I could also just look at the file size: at night the images are mostly > black, which compresses to a very small file size. > > Comments are welcome, > > Thanks, > > Andrew > > >
