关于python：PiCamera Flask，启停预览

PiCamera Flask, start and stop preview

我正在 Flask 中创建一个小的 Web 界面，以使用 PiCamera python 模块控制 Raspberry Pi 相机。我有一个显示来自相机的流的工作索引页面。但是，当我通过输入按钮发布 stop_preview() 时，应用程序失败，我无法弄清楚我做错了什么。到目前为止，这是我的一些代码。

这是我的观点的一部分。py

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from flask import redirect, url_for, session, request, //
render_template, Response
from simplepam import authenticate
from app.camera_pi import Camera
from app import app

@app.route(‘/’, methods=[‘GET’, ‘POST’])
@app.route(‘/index’, methods=[‘GET’, ‘POST’])
def index():
if request.method == ‘POST’:
if request.form[‘submit’]:
Camera.StopPreview()
elif request.method == ‘GET’:
return render_template("index.html", title="Home")

def gen(camera):
"""Video streaming generator function."""
while True:
frame = camera.get_frame()
yield (b‘–frame/
/
‘
b‘Content-Type: image/jpeg/
/
/
/
‘ + frame + b‘/
/
‘)

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

这是我的 index.html 模板。

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<!DOCTYPE html>

这是 camera_pi.py 文件(取自 Miguel Grinberg 的 github 存储库 https://github.com/miguelgrinberg/flask-video-streaming)

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# The MIT License (MIT)
#
# Copyright (c) 2014 Miguel Grinberg
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the"Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED"AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

import time
import io
import threading
import picamera
from app import camera_config

class Camera(object):
thread = None # background thread that reads frames from camera
frame = None # current frame is stored here by background thread
last_access = 0 # time of last client access to the camera
stop_camera = False

def initialize(self):
if Camera.thread is None:
# start background frame thread
Camera.thread = threading.Thread(target=self._thread)
Camera.thread.start()

# wait until frames start to be available
while self.frame is None:
time.sleep(0)

def get_frame(self):
Camera.last_access = time.time()
self.initialize()
return self.frame

def StopPreview():
Camera.stop_camera = True

@classmethod
def _thread(cls):
with picamera.PiCamera() as camera:
# camera setup
camera.resolution = camera_config.camera_resolution

# let camera warm up
camera.start_preview()
time.sleep(2)

stream = io.BytesIO()
for foo in camera.capture_continuous(stream, ‘jpeg’,
use_video_port=True):
# store frame
stream.seek(0)
cls.frame = stream.read()

# reset stream for next frame
stream.seek(0)
stream.truncate()

# if there hasn’t been any clients asking for frames in
# the last 10 seconds stop the thread
if time.time() – cls.last_access > 10:
break
elif Camera.stop_camera is True:
break
cls.thread = None

我添加了”def StopPreview()”部分，当我从索引页面发布提交按钮时，它被调用，但此时应用程序崩溃了。

提前感谢您提供的任何帮助。

首先，picamera的start_preview和stop_preview方法只是启动和停止预览，也就是出现在Pi自带显示器上的叠加视频。这些方法不会启动或停止相机本身。

要停止摄像头，您必须让方法 _thread 中的后台线程退出，这与它在 10 秒不活动过去时退出的方式类似。

例如，您可以向对象添加一个 stop_camera 变量，并使用 False 进行初始化。在您的停止方法中，您只需将变量翻转为 True 并返回。然后在后台线程中，根据条件中此变量的值添加第二个条件，检查 10 秒的非活动状态。

希望这会有所帮助！

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/267890.html

关于python：PiCamera Flask，启停预览

PiCamera Flask, start and stop preview

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