如何从烧瓶关闭OpenCV视频流

Question

我已经实施了一个系统，可以使用烧瓶和OpENCV从实时流捕获面孔。我现在面临关闭流并发布videocapture对象的困难。这是下面我的代码的片段：

from flask import Flask, Response, render_template
import cv2, imutils
import face_recognition
from skimage.exposure import is_low_contrast

app = Flask(__name__)

cam_feed = cv2.VideoCapture(0) # to get feed from webcam, use 0 as argument


def gen_frames():  # generate frame by frame from camera
    """
    Variable for counting number of images collected
    List for saving encodings also declared here
    """
    image_counter = 0

    name = "John Doe"
    known_names = []
    known_encodings = []


    if not cam_feed.isOpened():
        print("Cannot open camera")
        exit()

    while True:
        # Capture frame-by-frame
        success, frame = cam_feed.read()  # read the camera frame
        if not success:
            print("Can't receive frame (stream end?). Exiting ...")
            break
        else:
            ret, frame = cam_feed.read()
            frame = imutils.resize(frame, width=640)
           
            # if frame is read correctly ret is True
            if not ret:
                print("Can't receive frame (stream end?). Exiting ...")
                break
            # Our operations on the frame come here

            else:
                # face location model can either be HOG or CNN but HOG is faster (but less accurate) and way better if you don't have a GPU   
                boxes = face_recognition.face_locations(frame, model='hog')

                if boxes: # if a face is detected
                    for (top, right, bottom, left) in boxes:
                        if (image_counter < 20):
                            cv2.rectangle(frame, (left, top), (right, bottom), (0, 255, 0), 2)
                            encodings = face_recognition.face_encodings(frame, boxes)
                            known_names.append(name)
                            known_encodings.append(encodings)
                            image_counter += 1
                    
                        else:
                            break # break while True loop and end stream
            
                ret, buffer = cv2.imencode('.jpg', frame) # encode the frame so that flask can return it as a response in bytes format
                frame = buffer.tobytes() # convert each frame to a byte object
                yield (b'--frame\r\n'
                    b'Content-Type: image/jpeg\r\n\r\n' + frame + b'\r\n')  # concat frame one by one and show result

以下是我的流媒体路线：

@app.route('/video_feed')
def video_feed():
    #Video streaming route. Put this in the src attribute of an img tag
    return Response(gen_frames(), mimetype='multipart/x-mixed-replace; boundary=frame')


@app.route('/')
def index():
    """Video streaming home page."""
    return render_template('index.html')

当我的图像计数达到20时，循环似乎不会破裂，因为我可以看到我的网络摄像头仍在运行。我试图做的是创建另一个路由，在其中我调用cam_feed.release（），然后使用我的index.html file file;这是代码：

@app.route('/done')
def done():
    if cam_feed.isOpened():
        print("Releasing cam feed")
        cam_feed.release()
    return "Done"

最后，这是运行烧瓶服务器的代码：

if __name__ == '__main__':
    app.run(debug=True)

我的问题是：在收集图像后，如何停止流并关闭网络摄像头？谢谢。

Answer 1

我认为这是因为您启用了烧瓶应用程序debug模式（app.run（debug = true）），默认情况下将使用Relioader模式。如果启用了重新加载模式，则您的烧瓶应用程序将被加载到单独的过程中，以便根据文件更改连续更新应用程序，这将导致cam_feed = cv.cv2.videocapture（0）正在正在在两个分离的处理（主和烧瓶应用程序）中两次运行。当您运行cam_feed.release（）时，它仅在运行烧瓶应用程序的过程中关闭CAM，而主进程仍然具有cam_feed打开。为了避免这种情况，您可以通过访问环境变量Werkzeug_run_main添加该过程是否为主要过程，该检查是主要进程独有的。

import os
if os.environ.get('WERKZEUG_RUN_MAIN'):
    cam_feed = cv2.VideoCapture(0)

此外，您还可以关闭debug模式（app.run（debug = false））并调用cam_feed = cv2.videocapture（0）就像您在原始代码中所做的一样

Answer 2

在每个请求中，您在后台运行的真实运行。

更改

while True:

为

while cap.isOpened()

并确保何时完成请求，

cap.release()

请在调用此方法时使用此方法发布资源，您的WARE循环在后台停止！