capture_camera.py

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# Example : capture an image from an attached camera

# Author : Toby Breckon, toby.breckon@durham.ac.uk

# Copyright (c) 2015 School of Engineering & Computing Science,
# Copyright (c) 2019 Dept Computer Science,
#                    Durham University, UK
# License : LGPL - http://www.gnu.org/licenses/lgpl.html

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import cv2
import argparse
import sys

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# parse command line arguments for camera ID or video file

parser = argparse.ArgumentParser(
    description='Perform ' +
    sys.argv[0] +
    ' example operation on incoming camera/video image')
parser.add_argument(
    "-c",
    "--camera_to_use",
    type=int,
    help="specify camera to use",
    default=0)
parser.add_argument(
    "-r",
    "--rescale",
    type=float,
    help="rescale image by this factor",
    default=1.0)
args = parser.parse_args()

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# define video capture object

try:
    # to use a non-buffered camera stream (via a separate thread)

    import camera_stream
    cap = camera_stream.CameraVideoStream(use_tapi=False)

except BaseException:
    # if not then just use OpenCV default

    print("INFO: camera_stream class not found - camera input may be buffered")
    cap = cv2.VideoCapture()

# define display window name

window_name = "Live Camera Input"  # window name

# open camera device (and check it worked)

if not (cap.open(args.camera_to_use)):
    print("Cannot open camera - check connection and operation as suggested.")
    sys.exit

# read an image from the camera

ret, frame = cap.read()

# to avoid the black/blank first frame from many cameras
# with some (not all) cameras you need to read the first frame twice
# (first frame only)

ret, frame = cap.read()

# check it has loaded

if frame is not None:

    # create window by name (as resizable)

    cv2.namedWindow(window_name, cv2.WINDOW_NORMAL)

    # display image

    cv2.imshow(window_name, frame)

    # start the event loop - essential
    # wait indefinitely for any key press

    cv2.waitKey(0)

else:
    print("No image successfully loaded from camera.")

# close all windows

cv2.destroyAllWindows()

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