Workaround the HDR bug of macOS Catalina 10.15.4

ToggleHDRCatalina.applescript

#!/usr/bin/osascript
tell application "System Preferences"
  activate
end tell

tell application "System Events"
  tell process "System Preferences"
    activate
    delay 1
    click menu item "Displays" of menu "View" of menu bar 1
    delay 1
    tell window "LG HDR 4K"
      delay 1
      if (exists tab group 1) then
        click radio button "Display" of tab group 1
        set HDRCheckbox to checkbox "High Dynamic Range" of tab group 1
        if (exists HDRCheckbox) then
          click HDRCheckbox
          tell HDRCheckbox
            if (its value as boolean) then
              delay 15
              click HDRCheckbox
            end if
          end tell
        end if
      end if
    end tell
  end tell
end tell

Thanks for the script, I've been doing these steps manually to fix the resolution. You can also add a shebang on top which makes it a bit easier to run #!/usr/bin/osascript

Hi! Haven't tested it yet, but seems great! My LG 4K (27UL850W) is ugly with HDR enabled, but sometimes worse with HDR disabled, this could be the Neon bug? It is like mike656 is describing as "256 colors". https://discussions.apple.com/thread/251213356

This script seems "just" to toggle HDRCheckbox, so it seems indeed the same as toggling it in system preferences, and this does not work for me (sometimes need to toggle 10 times on/off before the 256 colors are gone; after sleep I have 256 colors again)

I would like to understand these problems and the script better. Is there anyone capable of explaining the HDR and 256 color (Neon?) bug and what this script does? Would appreciate a lot!!

BTW, I run 10.15.6; monitor is hooked-up via Displayport on RX580

@nicolas-martin Added. Thanks for the suggestion! BTW, @lexrus is the original author so the thanks should go to him.

@mhschaap The script is just an automation of toggling the HDR checkbox for convenience. I normally run it every time I wake my laptop up from sleep. Note that if your HDR checkbox is already off when you wake up your MBP, then you need to turn it on and then turn it off again. From doing this lots of times, it seems that you need to wait a few seconds in between, otherwise there's a higher chance it won't work, so the script does just that: turns on HDR, waits 15 seconds, turns it off.

If it's not working for you, then maybe you're closing the settings window before the script gets a chance to finish ?

Hi @adriang133, your script is far more stable than mine. 👍
But I just ended up bought another 4K display without so-called HDR. What a life saving. 😄

If it's not working for you, then maybe you're closing the settings window before the script gets a chance to finish ?

Hi @adriang133; it works! I have saved it as an application, moved it to /Applications (sudo) and added it to the login applications. So it starts automatically at login. Could the preferences screen also be closed automatically? click menu item "Displays" of menu "View" of menu bar 1; but then afterwards close?

See ToggleHDRCatalina on the screenshot

Added October 4th 2020:
been using it for quite a while now and in principle it works, however: after completion of the script, I need to power-off the monitor, by the joystick-button and power it on again. Without this action it does not work.
Still I am quite happy with the script! so Thanks!!

The script is fine, but still I had some issues left; making a custom EDID file and putting this in /S/L/Displays..../Overrides completely disables HDR; so no script to be run and no flickering. This may interest other readers: https://www.tonymacx86.com/threads/10-15-4-update-how-to-disable-hdr-support.293991

However, if you would like to keep HDR as an option, you should use this script. I don't need HDR. Thanks @adriang133