how can i publish and subscribe an image (using mqtt in python) - mqtt

Question

I use Baidu loT Core. I use two devices as clients, a database(TSDB) as server. The target function:One client send a image to database , then data bese transmits to another client. I get help from How can I publish a file using Mosquitto in python?
but it still doesn't work.
send image
import paho.mqtt.client as mqtt
import json
import cv2
HOST = '************'
PORT = 1883
client_id = '************'
username = '***********'
password = '******************'
topic = '******'
# obj = userdata
# mqttc = client
def on_connect(mqttc, obj, flags, rc):
print("rc: " + str(rc))
def on_message(mqttc, obj, msg):
print(msg.topic + " " + str(msg.qos) + " " + str(msg.payload.decode('utf-8')))
def on_publish(mqttc, obj, mid):
print("mid: " + str(mid))
def on_subscribe(mqttc, obj, mid, granted_qos):
print("Subscribed: " + str(mid) + " " + str(granted_qos))
def on_log(mqttc, obj, level, string):
print(string)
def on_disconnect(mqttc, obj, rc):
print("unsuccess connect %s" % rc)
mqttc = mqtt.Client(client_id)
mqttc.username_pw_set(username, password) # thanks correction. I found I forget to connect broker.But the question is still
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_publish = on_publish
mqttc.on_subscribe = on_subscribe
mqttc.on_disconnect = on_disconnect
# Uncomment to enable debug messages
mqttc.on_log = on_log
mqttc.connect(HOST, PORT, 60)
image = 'E:/_TempPhoto/0.jpg'
print(type(image))
def imageToStr(image):
with open(image, 'rb') as f:
image_byte = base64.b64encode(f.read())
print(type(image_byte))
image_str = image_byte.decode('ascii') # byte to str
print(type(image_str))
return image_str
image1 = imageToStr(image)
data = {
"engineeringdata": {
"date": 12,
"value": "59.3;98.5",
"image": image1
}
}
json_mod = json.dumps(data)
mqttc.publish(topic, json_mod, 0)
mqttc.loop_forever()
receive image
import paho.mqtt.client as mqtt
import cv2
import numpy as np
import json
HOST = '*********'
PORT = 1883
client_id = '************'
username = '*****************'
password = '******************'
topic = '***************'
def on_connect(client, userdata, flags, rc):
print("Connected with result code: " + str(rc))
def strToImage(str,filename):
image_str= str.encode('ascii')
image_byte = base64.b64decode(image_str)
image_json = open(filename, 'wb')
image_json.write(image_byte) #将图片存到当前文件的fileimage文件中
image_json.close()
def on_message(client, userdata, msg):
print(msg.topic + " " + str(msg.payload))
strToImage(str(msg.payload), 'E:/_TempPhoto/restore001.jpg')
client = mqtt.Client(client_id)
client.username_pw_set(username, password)
client.on_connect = on_connect
client.connect(HOST, PORT, 60)
client.subscribe(topic, 0)
client.on_message = on_message
client.loop_forever()
# while True:
# client.loop(15)
# time.sleep(2)
This is my send image 's message and log. I moit a part of printed data of image by '......'
Sending CONNECT (u1, p1, wr0, wq0, wf0, c1, k60) client_id=b'client_for_test'
<class 'str'>
<class 'bytes'>
<class 'str'>
Sending PUBLISH (d0, q0, r0, m1), 'b'$iot/client_for_test/user/fortest'', ... (102800 bytes)
mid: 1
Received CONNACK (0, 0)
rc: 0
Sending PINGREQ
Received PINGRESP
Sending PINGREQ
Received PINGRESP
this is receive image 's printed message:(seems right)
Connected with result code: 0
My error case is 5. And I didn't recvice a image. But it seemed that send successfully.
Maybe it's because the send image send once and end, but the receive image can't receive rightly.
I just need the most simple codes of two clients to send and receive the image through mqtt,please!
Give me a hand!
Thanks for help. The previous problems have been solved. But there has new trouble. I edit the new codes, I couldn't receive the image.
please, Correct my code.

Answer 1

you can encode the image to base64 before publishing it so the topic's content will be a string, example:
import base64
with open("t.png", "rb") as imageFile:
str = base64.b64encode(imageFile.read())
print str

Answer 2

Publisher.py
import paho.mqtt.publish as publish
f= open("myimage.jpg")
content = f.read()
mybyteArray = bytearray(content)
mqttc.publish(topic, mybyteArray , 1)
Receiver.py
def on_message(client, userdata, msg):
f = open('myReceivedImage.jpg','w')
f.write(msg.payload)
f.close()