Writing the ESP32 firmware, with all its timing critical constraints, was only half of the job, the actual image generation happens on an MQTT server (hosted on a Raspberry Pi). I've made one of my most complex flows:

It does the following things:

• Fetch the data from different sources (weather data, public transport, Bitcoin value)
• Parse the data according to selected display
• Evaluate the screen update rate (the ESP32 sends back a "heartbeat" message every time it is updated)
• Ping the matrix to make sure it is present
• Send the data to MQTT only if the pixels have changed and the matrix has been successfully pinged
• Apply a "brightness filter" to set the pixel intensity level according to the user settings
• Compress the data to a binary stream for efficient transport (as efficient as it can be made with this framework...)
• Update the Node-RED user interface

In the user interface one can:

• See the preview of what is currently displayed
• Select the matrix display
• Set the LED brightness
• Change the display every minute (selects the next one in the list)
• Turn off the LED matrix (send a black screen and then stop sending updates)
• Show the connection state (ESP32 IP ping status)