control macos brightness of monitor(s) via MIDI input

midi-brightness.py

#!/usr/bin/env python3

# launch with `uv run`. https://docs.astral.sh/uv/
# uses https://github.com/waydabber/betterdisplay/ to control the monitors


# /// script
# dependencies = [
#     "python-rtmidi==1.5.8",
#     "requests==2.32.4",
# ]
# ///

import requests 
import rtmidi
import subprocess
import sys
import time
from contextlib import contextmanager


@contextmanager
def timer(label):
    start = time.perf_counter()
    try:
        yield
    finally:
        print(f"{label} took {time.perf_counter() - start:.4f} seconds")


# MIDI CC to display mapping (adjust these for your setup)
CC_TO_DISPLAY = {
    # vertical monitor is ID = 3
    72: 3,
    76: 3,

    # top
    73: 1,
    # bottom
    77: 2,
}

def set_brightness(display, brightness):
    # curl -X GET -G http://localhost:55777/set -d "brightness=80%" -d "displayID=1"
    requests.get("http://localhost:55777/set", 
                 params={"displayID": display,
                         "brightness": brightness})

    
def midi_callback(message, data):
    msg, deltatime = message
    # print(msg)
    if len(msg) == 3 and msg[0] == 0xB0:  # Control Change on channel 1
        cc_number = msg[1]
        cc_value = msg[2]
        
        if cc_number in CC_TO_DISPLAY:
            display = CC_TO_DISPLAY[cc_number]
            brightness = cc_value / 127
            set_brightness(display, brightness)
            # print(f"CC {cc_number} → Display {display}: {brightness}")

def main():
    midi_in = rtmidi.MidiIn()
    
    # Find LPD8 port
    ports = midi_in.get_ports()
    lpd8_port = None
    
    for i, port in enumerate(ports):
        if "LPD8" in port or "Akai" in port:
            lpd8_port = i
            break
    
    if lpd8_port is None:
        print("LPD8 not found. Available ports:")
        for i, port in enumerate(ports):
            print(f"  {i}: {port}")
        sys.exit(1)
    
    print(f"Connecting to: {ports[lpd8_port]}")
    midi_in.open_port(lpd8_port)
    midi_in.set_callback(midi_callback)
    
    print("MIDI brightness control running... Press Ctrl+C to stop")
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        print("\nShutting down...")
    finally:
        midi_in.close_port()

if __name__ == "__main__":
    main()


# Tried to have this auto start but couldn't get it working in 20 minutes, so I just launch it myself in a terminal window like an animal ¯\_(ツ)_/¯


# PLISTPATH=~/Library/LaunchAgents/com.keminglabs.midi-brightness.plist
# cat << 'EOF' > $PLISTPATH

# <?xml version="1.0" encoding="UTF-8"?>
# <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
# <plist version="1.0">
# <dict>
#     <key>Label</key>
#     <string>com.keminglabs.midi-brightness</string>
#     <key>ProgramArguments</key>
#     <array>
#         <string>/Users/dev/.dotfiles/uv_shim</string>
#         <string>run</string>
#         <string>/Users/dev/.dotfiles/bin/midi-brightness.py</string>
#     </array>
#     <key>RunAtLoad</key>
#     <true/>
#     <key>KeepAlive</key>
#     <true/>
#     <key>StandardOutPath</key>
#     <string>/Users/dev/Library/Logs/midi-brightness.log</string>
#     <key>StandardErrorPath</key>
#     <string>/Users/dev/Library/Logs/midi-brightness.log</string>
# </dict>
# </plist>
# EOF

# launchctl load -w $PLISTPATH