I am creating a little web interface in Flask to control the Raspberry Pi camera using the PiCamera python module. I have a working index page which displays a stream from the camera. However, when I POST stop_preview() via an input button the app fails and I cannot work out what I am doing wrong. Here's some of my code so far.
This is part of my views.py
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'--framern'
b'Content-Type: image/jpegrnrn' + frame + b'rn')
@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')
This is my index.html template.
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<img id="video_feed" src="{{ url_for('video_feed') }}">
<form method="post">
<p><input type="submit" name="submit" value="StopPreview"></p>
</form>
</body>
</html>
This is the camera_pi.py file (taken from Miguel Grinberg's github repo https://github.com/miguelgrinberg/flask-video-streaming)
# 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
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():
with picamera.PiCamera() as camera:
camera.stop_preview()
@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
cls.thread = None
I have added the "def StopPreview()" section and it is being called when I POST a submit button from the index page, but the app just crashes at this point.
Thanks in advance for any help you can provide.
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