Python MQTT 发布 JSONified Numpy 数组

Question

我目前正在实现在两个树莓派之间使用的 MQTT 协议。第一个是 Pi 0，将连接一个 pi 相机。它将每个捕获的帧转换为 numpy 数组，然后将其发布到主 Pi，然后使用 PIL 将 numpy 数组转换为图像。我这样做是因为我希望在主 Pi 上执行主要的图像处理操作。

我的问题是主 Pi 没有收到任何消息。我已经进行了调试，并且在服务脚本上一切正常。但是由于某种原因，主 Pi 没有收到任何内容。

这是两个脚本：

servant.py：

import paho.mqtt.client as mqtt
import time
import cv2
import numpy
import json

MQTT_SERVER = "iot.eclipse.org"
MQTT_PATH = "test_channel"

mqttc = mqtt.Client()
mqttc.connect(MQTT_SERVER, 1883, 60)

cap = cv2.VideoCapture(0)

while True:
    ret, frame = cap.read()
    frame_list = frame.tolist()
    MQTT_MESSAGE = json.dumps(frame_list)
    mqttc.publish(MQTT_PATH, MQTT_MESSAGE)
    time.sleep(1)

ma​​ster.py：

import paho.mqtt.client as mqtt
import numpy as np
import json
import PIL

MQTT_SERVER = "iot.eclipse.org"
MQTT_PATH = "test_channel"

def on_connect(client, userdata, flags, rc):
    print("connected with result code " + str(rc))
    client.subscribe(MQTT_PATH)

def on_message(client, userdata, msg):
    data = json.loads(msg.payload)
    array = np.array(data)
    img = PIL.Image.fromarray(array)
    cv2.imshow('image', img)
    cv2.waitKey()

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(MQTT_SERVER, 1883, 60)

client.loop_forever()

Answer 1

在您的发布代码中，您实际上并没有给客户端任何时间来处理它尝试发送的消息。这甚至是一个更大的问题，因为消息可能比单个网络数据包（作为图像）大。要解决此问题，您必须调用 MQTT 客户端循环函数（或在 b

import paho.mqtt.client as mqtt
import time
import cv2
import numpy
import json

MQTT_SERVER = "iot.eclipse.org"
MQTT_PATH = "test_channel"

mqttc = mqtt.Client()
mqttc.connect(MQTT_SERVER, 1883, 60)

cap = cv2.VideoCapture(0)

while True:
    ret, frame = cap.read()
    frame_list = frame.tolist()
    MQTT_MESSAGE = json.dumps(frame_list)
    mqttc.publish(MQTT_PATH, MQTT_MESSAGE)
    mqttc.loop()
    time.sleep(1)

或者像这样：

import paho.mqtt.client as mqtt
import time
import cv2
import numpy
import json

MQTT_SERVER = "iot.eclipse.org"
MQTT_PATH = "test_channel"

mqttc = mqtt.Client()
mqttc.connect(MQTT_SERVER, 1883, 60)

cap = cv2.VideoCapture(0)

mqttc.start_loop()

while True:
    ret, frame = cap.read()
    frame_list = frame.tolist()
    MQTT_MESSAGE = json.dumps(frame_list)
    mqttc.publish(MQTT_PATH, MQTT_MESSAGE)
    time.sleep(1)