Python opencv和多处理 [英] Python opencv and multiprocessing

问题描述

我正在寻找使用python的多处理模块来创建一个进程，该进程通过opencv的python界面不断轮询网络摄像头，并将生成的图像发送到队列中，其他进程可以从中访问它们.但是，每当我尝试对其他进程从队列中检索到的图像执行任何操作时，都会遇到挂起(Ubuntu 12.04上为python 2.7)的情况.这是一个最小的示例:

I'm looking to use the multiprocessing module for python to create one process that continually polls a webcam via opencv's python interface, sending any resulting images to a queue from which other processes can access them. However, I'm encountering a hang (python 2.7 on Ubuntu 12.04) whenever I try to do anything with the images retrieved by other processes from the queue. Here's a minimal example:

import multiprocessing
import cv

queue_from_cam = multiprocessing.Queue()

def cam_loop(queue_from_cam):
    print 'initializing cam'
    cam = cv.CaptureFromCAM(-1)
    print 'querying frame'
    img = cv.QueryFrame(cam)
    print 'queueing image'
    queue_from_cam.put(img)
    print 'cam_loop done'


cam_process = multiprocessing.Process(target=cam_loop,args=(queue_from_cam,))
cam_process.start()

while queue_from_cam.empty():
    pass

print 'getting image'
from_queue = queue_from_cam.get()
print 'saving image'
cv.SaveImage('temp.png',from_queue)
print 'image saved'

此代码应运行到保存图像"的打印状态，然后挂起.有什么想法可以解决这个问题吗?

This code should run up to the print out of "saving image" but then hang. Any ideas how I can go about fixing this?

推荐答案

最简单的方法是使用基于NumPy数组的更新的cv2模块.这样一来，您就不必再为手工腌制而烦恼了.解决方法如下(我刚刚更改了4行代码):

The simplest approach is to use the newer cv2 module that's based on NumPy arrays. That way you don't have to mess with manual pickling. Here's the fix (I just changed 4 lines of code):

import multiprocessing
import cv2

queue_from_cam = multiprocessing.Queue()

def cam_loop(queue_from_cam):
    print 'initializing cam'
    cap = cv2.VideoCapture(0)
    print 'querying frame'
    hello, img = cap.read()
    print 'queueing image'
    queue_from_cam.put(img)
    print 'cam_loop done'

cam_process = multiprocessing.Process(target=cam_loop,args=(queue_from_cam,))
cam_process.start()

while queue_from_cam.empty():
    pass

print 'getting image'
from_queue = queue_from_cam.get()
print 'saving image'
cv2.imwrite('temp.png', from_queue)
print 'image saved'

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