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opencv python camera frame grab and display on different threads with safe synchronization
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#!/usr/bin/env python | |
from threading import Thread, Lock | |
import cv2 | |
class WebcamVideoStream : | |
def __init__(self, src = 0, width = 320, height = 240) : | |
self.stream = cv2.VideoCapture(src) | |
self.stream.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, width) | |
self.stream.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, height) | |
(self.grabbed, self.frame) = self.stream.read() | |
self.started = False | |
self.read_lock = Lock() | |
def start(self) : | |
if self.started : | |
print "already started!!" | |
return None | |
self.started = True | |
self.thread = Thread(target=self.update, args=()) | |
self.thread.start() | |
return self | |
def update(self) : | |
while self.started : | |
(grabbed, frame) = self.stream.read() | |
self.read_lock.acquire() | |
self.grabbed, self.frame = grabbed, frame | |
self.read_lock.release() | |
def read(self) : | |
self.read_lock.acquire() | |
frame = self.frame.copy() | |
self.read_lock.release() | |
return frame | |
def stop(self) : | |
self.started = False | |
self.thread.join() | |
def __exit__(self, exc_type, exc_value, traceback) : | |
self.stream.release() | |
if __name__ == "__main__" : | |
vs = WebcamVideoStream().start() | |
while True : | |
frame = vs.read() | |
cv2.imshow('webcam', frame) | |
if cv2.waitKey(1) == 27 : | |
break | |
vs.stop() | |
cv2.destroyAllWindows() |
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