where does pix_image look for the image file that it will open? i've tried a few places to no avail.

Wherever you tell it to. You must send a message, like this:
open /users/you/pictures/somepicture.jpg

The openpanel object is useful here, I would say "It's all in the documentation, but the GEM examples are somewhat more complicated than they need to be.

thank you for the information...as you can see i am the newest of newbies. i'm trying to rewrite a max/msp jitter patch for pd that scans the visual field of a vcamera for changes (ie movement and position etc) and most of it was jittered. ah, the learning curve.
thanks again
i'll get right on it

Is a vcamera an external video device? For webcams, dv cams and the like, you can use [pix_video].