# 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 :ref:`docs/software/vision-processing/introduction/cameraserver-class:Read and Process Video: CameraServer Class`.

.. tab-set-code::

   ```py
   from cscore import CameraServer
   import cv2
   import numpy as np
   CameraServer.enableLogging()
   camera = CameraServer.startAutomaticCapture()
   camera.setResolution(width, height)
   sink = CameraServer.getVideo()
   input_img = np.zeros(shape=(height, width, 3), dtype=np.uint8)
   while True:
      time, input_img = sink.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.

.. image:: images/image-thresholding/target.jpg
   :alt: 2020 game target with the retroreflective tape illuminated green.

## 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 Elastic.

.. tab-set-code::

   ```py
   #
   # CameraServer initialization code here
   #
   output = CameraServer.putVideo("Name", width, height)
   input_img = np.zeros(shape=(height, width, 3), dtype=np.uint8)
   while True:
      time, input_img = sink.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.

.. image:: images/using-cameraserver/red-outline.jpg
   :alt: Image above with the target outlined in red by the algorithm.