# This script shows how to open a camera in OpenCV and grab frames and show these.
# Kim S. Pedersen, 2022

import cv2 # Import the OpenCV library


def gstreamer_pipeline(capture_width=1024, capture_height=720, framerate=30):
    """Utility function for setting parameters for the gstreamer camera pipeline"""
    return (
        "libcamerasrc !"
        "video/x-raw, width=(int)%d, height=(int)%d, framerate=(fraction)%d/1 ! "
        "videoconvert ! "
        "appsink"
        % (
            capture_width,
            capture_height,
            framerate,
        )
    )


print("OpenCV version = " + cv2.__version__)

# Open a camera device for capturing
cam = cv2.VideoCapture(gstreamer_pipeline(), apiPreference=cv2.CAP_GSTREAMER)


if not cam.isOpened(): # Error
    print("Could not open camera")
    exit(-1)

# Open a window
WIN_RF = "Example 1"
cv2.namedWindow(WIN_RF)
cv2.moveWindow(WIN_RF, 100, 100)


while cv2.waitKey(4) == -1: # Wait for a key pressed event
    retval, frameReference = cam.read() # Read frame
    
    if not retval: # Error
        print(" < < <  Game over!  > > > ")
        exit(-1)
    
    # Show frames
    cv2.imshow(WIN_RF, frameReference)
    

# Finished successfully