I have an app [..], and when I connect it "/ros_camera_preview_view" appears when I use "rosnode list" I've searching the web but I can't find any documentation for this /ros_camera_preview_view node?
/ros_camera_preview_view is the name, not a node type, so unless the name is exactly identical to the type, chances are you won't find anything when searching for the name.
I have an app [..]
Since you mention "app", I assume you're running this on a phone. I'd try to get some more info from whoever / wherever you got the app.
If that is not possible, try doing a rosnode info /ros_camera_preview_view and see what the ROS API is that the node exposes (ie: topics, services, actions, etc).
Then for each of the topics listed, do a rostopic info <topic_name> and a rostopic type <topic_name> (there should be tab-completion). That should help you figure out the types that are being used. Do the same for any services, but use rosservice info <service_name> and rosservice type <service_name>.
How would I retrieve images in this node in C++ code?
Seeing as you mention "sends images to Ros", I'm going to guess it has at least one topic onto which sensor_msgs/Images are being published (or any of the compressed versions). In that case, you'll want to check Writing a Simple Image Subscriber (Python version here).
when I try to include "ros_camera_preview_view" Ros will tell me that the package doesn't exist?
That's not how this works, but that will probably become clear from the tutorial(s) I linked.
