Software Overview
The SDK contains a superinterface called CameraControl, which contains 5 interfaces:
Similar to Java classes, Java interfaces provide methods. A webcam can be controlled using methods of these 5 interfaces.
PtzControl allows control of 3 related features: virtual pan, tilt and zoom. ExposureControl also contains a feature called auto-exposure priority, or AE Priority. Together there are 8 camera controls discussed in this tutorial.
The official documentation is found in the Javadocs. Click the link for RobotCore, then click the CameraControl link in the left column.
RobotCore Javadoc API
That page provides links to the 5 interfaces listed above.
The methods described here can be used in Android Studio, OnBot Java or Blocks.
You will see VisionPortal mentioned here, and in the sample OpModes. Why VisionPortal? These controls act on a camera that is already open and streaming, and in the SDK it’s the VisionPortal that opens the camera and manages its stream. So the Portal is also where you ask for a control object:
myExposureControl = visionPortal.getCameraControl(ExposureControl.class);
A Portal can be built with no vision processor at all, which is enough to open the camera and show its LiveView preview while you experiment with these controls.
These CameraControl interfaces allow some control of the webcam, within requirements or settings of the VisionPortal for its own performance. Such settings include resolution and frame rate, not covered here.