Change screen to black and white for accessibility reasons

I need help changing my screen to black and white, but in a specific way. On GIMP, you can desaturate the colours based on Lightness (2) and Luminosity (3). I need my entire screen to be converted to greyscale 'based on luminosity'. Is there a way I can do this with Xorg or some other program? An example of how I need the colors converted

Know someone who can answer? Share a link to this question via email, Twitter, or Facebook.