Using CameraServer

Grabbing Frames from CameraServer

The WPILibPi image comes with all the necessary libraries to make your own vision processing system. In order to get the current frame from the camera, you can use the CameraServer library. For information about CameraServer, the Read and Process Video: CameraServer Class.

from cscore import CameraServer
import cv2
import numpy as np

cs = CameraServer.getInstance()
cs.enableLogging()

camera = cs.startAutomaticCapture()
camera.setResolution(width, height)

sink = cs.getVideo()

while True:
   time, input_img = cvSink.grabFrame(input_img)

   if time == 0: # There is an error
      continue

Note

OpenCV reads in the image as BGR, not RGB for historical reasons. Use cv2.cvtColor if you want to change it to RGB.

Below is an example of an image that might be grabbed from CameraServer.

../../../../_images/using-cameraserver-1.jpg

Sending frames to CameraServer

Sometimes, you may want to send processed video frames back to the CameraServer instance for debugging purposes, or viewing in a dashboard application like Shuffleboard.

#
# CameraServer initialization code here
#

output = cs.putVideo("Name", width, height)

while True:
   time, input_img = cvSink.grabFrame(input_img)

   if time == 0: # There is an error
      output.notifyError(sink.getError())
      continue

   #
   # Insert processing code here
   #

   output.putFrame(processed_img)

As an example, the processing code could outline the target in red, and show the corners in yellow for debugging purposes.

Below is an example of a fully processed image that would be sent back to CameraServer and displayed on the Driver Station computer.

../../../../_images/using-cameraserver-2.jpg