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
