Webcam image intensity acquisition

[AlexZLee]

Hi,

I am trying to use a webcam to acquire a real time video (image) and simultantously plot out the grey scale intensity from this image. The real time video part is easy and there is no problem. I started working one extracting intensity by looking at the Labview built in example called "Light Meter", which I also attached. When I compiled these two VI together, the VI did not report any error, but the grey scale intensity always stay at 0.

I have attached my VI and anyone who have experience please help me. I saw several related posts on this forum but looks like it is unsolved. Seems many people is working on similar project. I guess it would be very helpful for a lot of people if this VI can finally work.

[AlexZLee]

Anyone has a thought?

[aflojo]

Would you mind sharing a sample image that you are trying to do this with?

[AlexZLee]

Sure!  For example,in the image below, I am trying to measure the grey value intensity of the rectanglar region. The whole idea is to use a webcam to measure the real time grey value intensity from the camera. But as you can see, it gives zero intensity, which does not make any sense 

[aflojo]

I cannot view the image attached, would you mind trying again?