使用python和flask实时更新ecg图表

Question

我已经创建了一个简单的python flask应用程序，用于与用于培训应急服务的训练模拟器进行交互。在这个应用程序中，我想要显示ECG波形和生命体征。我能够使用chartjs实现这一点，但是它非常慢，因此不适合我的需求。我创建了一个线程类，它使用flask-socketio定期将波形数据点提供给我的javascript。在socketio事件中，将调用用于更新图表的javascript函数。我对所有这些技术都是新手，我想知道我是不是在线程方面做错了什么，或者滥用了socketio，或者可能是chartjs或flask，这些都不是我应该用来实现我的目标的。请建议我如何提高图表更新的性能，以便我可以在浏览器应用程序上显示典型的ECG波形，就像您在医院的ECG机器上看到的那样。

app9.py (主应用程序)：

from flask_socketio import SocketIO, emit
from flask import Flask, render_template, url_for, 
copy_current_request_context, Markup
from random import random
from time import sleep
from threading import Thread, Event
import pylab
import scipy.signal as signal
import numpy as np
from itertools import cycle
from flask_bootstrap import Bootstrap

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
app.config['DEBUG'] = True

#turn the flask app into a socketio app
socketio = SocketIO(app)

#random number Generator Thread
thread = Thread()
thread_stop_event = Event()


class ECGThread(Thread):
    def __init__(self):
        self.delay = 1
        super(ECGThread, self).__init__()

    def waveformGenerator(self):
        #infinite loop of pqrst
        print("Generating waveform")
        i=0
        pqrst = signal.wavelets.daub(10)
        pqrst_list = pqrst.tolist()
        while not thread_stop_event.isSet():
            for i in cycle(pqrst_list):
                data=i
                socketio.emit('ecg-update', {'data': data})
                #print('emitted: ' + str(data))
            sleep(self.delay)

    def run(self):
        self.waveformGenerator()


@app.route('/')
def index():
#only by sending this page first will the client be connected to the 
socketio instance
    return render_template('index9.html')

@socketio.on('connect')
def test_connect():
    # need visibility of the global thread object
    global thread
    print('Client connected')

    #Start the waveform generator thread only if the thread has not been 
    started before.
    if not thread.isAlive():
        print("Starting Thread")
        thread = ECGThread()
        thread.start()

@socketio.on('disconnect')
def test_disconnect():
    print('Client disconnected')


if __name__ == '__main__':
    socketio.run(app,debug=True, host='0.0.0.0')

main9.js (用于处理ecg图表的javascript)：

// function to add data to a chart
function addData(chart, label, data){
    chart.data.labels.push(label);
    chart.data.datasets.forEach((dataset) => {
    dataset.data.push(data);
    });
    chart.update();
}

// function to remove data to a chart
function removeData(chart){
    chart.data.labels.pop();
    chart.data.datasets.forEach((dataset) => {
        dataset.data.pop();
    });
    chart.update()
}


// ECG Chart
var ecgChart = document.getElementById("ecgChart");

    var ecgChart = new Chart(ecgChart, {
        type: 'line',
        data: {
            labels:["1","2","3","4","5","6","7","8","9","10"],
            datasets: [
            {
                label: "My First Dataset",
                fill: false,
                lineTension: 0.1,
                backgroundColor: "rgba(75,192,192,0.4)",
                borderColor: "rgba(75,192,192,1)",
                borderCapStyle: 'butt',
                borderDash: [],
                borderDashOffset: 0.0,
                borderJoinStyle: 'miter',
                pointBorderColor: "rgba(75,192,192,1)",
                pointBackgroundColor: "#fff",
                pointBorderWidth: 1,
                pointHoverRadius: 5,
                pointHoverBackgroundColor: "rgba(75,192,192,1)",
                pointHoverBorderColor: "rgba(220,220,220,1)",
                pointBorderWidth: 2,
                pointRadius: 1,
                pointHitRadius: 10,
                data: [0.18817680007769047, 0.527201188931723, 
                       0.6884590394536007, 0.2811723436605783, 
                      -0.24984642432731163, -0.19594627437737416, 
                       0.1273693403357969, 0.09305736460357118, 
                      -0.0713941471663973,-0.02945753682187802]
            }]
        }
    });

// connect to the socket server.
var socket = io.connect('http://' + document.domain + ':' + 
location.port);

// receive details from server
socket.on('ecg-update', function(msg) {
    number = msg.data
    console.log(msg.data);
    addData(ecgChart,'new data', msg.data);
    removeData(ecgChart);
});

index9.html (HTML)：

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <meta http-equiv="x-ua-compatible" content="ie=edge">
        <title>{{ title }}</title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-
        scale=1">
        <script src="http://code.jquery.com/jquery-2.1.1.min.js">
        </script>
        <link rel="stylesheet" href="/static/normalize.css">
        <link rel="stylesheet" href="/static/main.css">

        <script type="text/javascript" 
        src="//cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.js">
        </script>
        <script type="text/javascript" 
src="//cdnjs.cloudflare.com/ajax/libs/socket.io/1.3.6/socket.io.min.js">
        </script>
        <script type="text/javascript" src="{{ url_for('static', 
filename='modernizr-3.6.0.min.js') }}"></script>

    </head>
    <body>
        <canvas id="ecgChart" width="600" height="400"></canvas>
        <script type="text/javascript" src="{{ url_for('static', filename='main9.js') }}"></script>
    </body>
</html>

Answer 1

我无法使用chart.js获得我想要的结果，但是我找到了两种方法来创建实时流传输心电图形。

1.)http://smoothiecharts.org/是制作实时流媒体图表的一个非常好和简单的工具，但是它不具备我想要的结果所需要的可定制性。

2.) http://theblogofpeterchen.blogspot.com/2015/02/html5-high-performance-real-time.html -我发现了一个博客，其中有人不使用任何绘图库来制作实时心电，而是编写了自己的构造函数来使用requestAnimationFrame()来制作实时图形。这就是我使用的。现在我只需要学习如何改变心率哈哈。

Answer 2

This webcomponent有惊人的应用编程接口。所有你需要做的就是在下一个节拍出现时运行回调

document.body.innerHTML += '<ecg-line></ecg-line>';
ecgLine((bang) => setInterval(() => bang(), 1000));

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