A scanner and a Web cam have standard interfaces; not so with digital cameras. If you look at what is offered you will see different solution for selected models of selected companies:
http://lmgtfy.com/?q=digital+camera+controlled+by+computer[
^], more likely of the Olympus, Casio or Canon brands, much less then others. Some Fuji cameras can work as a Web camera; and they have a switch in their menu; they work either in control mode or as a file system, for picture downloads; they also can implement interface for printing without a computer.
Try to find documentation of software for the model you have, this is the best you can do.
—SA
Submit an article or tip