Unhappy Take picture from USB Webcam

Dear Developers.

I have a little experience with Android Application development. Now, I start with new R&D project. I do the research and do Google for few week but found nothing.

With the new USBManager interface of android, I can see some attached usb device, but that is not enough.
I see some information about the Picture Transfer protocol, but do not know how to use.

Let me summary, I have a android device with OTG connector and a USB webcam. Please give me some help to take a picture from that webcam in my Android application.

Any help will be appreciated.
Happy coding.