You can use the Black Screen Detection Transform to detect a black screen image from a Webcam or similar source. A black screen is defined as an image darker than the specified Brightness Threshold. Below is a typical configuration:
Black Screen Detection Transform connected to WebCam Transform
BSD Capture: A transition on this event port causes the image from the BSD Source port to be transmitted from the BSD Snapshot port. The captured image is not necessarily a black screen.
BSD Enable: When this Boolean port is true, black screen detection is active. When false, the transform does not transmit any output.
BSD Snapshot: When a transition is received on the BSD Capture port, the current image is transmitted from this MxV Image port.
BSD Detect: This Boolean port is set to true when a black screen is detected.
Set the properties on the Black Screen Detector Transform as shown here:
Black Screen Detection Transform Properties
1.Click the Device Test verb to see the current image.
2.Select the camera from the drop-down list under the image.
Note: If the camera is not set up correctly, it will display Camera Not Ready.
3.Point the camera at an example of a black screen.
4.Use the slider to find the Brightness Threshold that produces 0% bright pixels.
5.Enter that value in the Brightness Threshold property.
When the Transform is used with a USB Webcam (Generic) Transform, the Webcam properties should be set as shown here:
Properties on the USB WebCam (Generic) Transform