How do I fire a camera connected on USB programatically?

I want to make something like they have at US dmv's where you sit down and it takes your picture, maybe like photobooth.

I want to connect a high end camera via usb, fire the camera开发者_运维知识库 and get the picture.

There's the Picture Transfer Protocol http://en.wikipedia.org/wiki/Picture_Transfer_Protocol a nastly little thing. All the cameras I held in my hands so far, claiming they had proper PTP support failed it somewhere. But in theory one can use PTP to remote control a camera, i.e. trigger the shutter, retrieve the picture and so on.

Rater than reimplementing the whole thing I recommend you get some readily usable PTP library. There are some open source ones listed on http://ptp.sourceforge.net

The easiest method is probably to use OpenCV: http://opencv.willowgarage.com/wiki/

If you need a high end camera - most digital SLRs have a tethered mode where you can control the camera, fire the shutter and retrieve the image data. Each camera maker has a proprietary (but normally free) sdk.

For a webcam type camera - these normally run in video mode, you simply grab an image out f the video stream - as PaulR says - use openCV