MaxLight

Alpha 1.0

This is a little tool to get the average screen color of a monitor of choice and send it to an rgb LED strip as fast as possible to tint a whole room in the displayed color.
It is not another copy of an Ambilight system, yet, but can be used for it if you'd assign Desktop-Areas to different LEDs and update the USB-buffer and Arduino code.
Instead, it's a room light to destress the eyes and raise the immersive power of entertainment setups and work spaces.
This is a quick/test setup for which i just dropped one LED strip behind my desk:

Keeping the CPU usage low was one of the goals, because gaming on my very own setup revealed:
my CPU is the performance bottleneck while the GPU stays cool and calm. A super low latency was important as well.

Using the program aka finding your preferred config.-values:

Make sure to install an USB-driver for the arduino. In my case it's the CH340-driver for the super cheap Arduino-Nano-Clone.
Your computer recognizes the device?
Load "lumos_maxima.cpp" onto your Arduino. ("Old Bootloader for ATMega" works for the AN-Clone)

Go ahead and run the program:

Inserting higher saturation and brightness values in the setup will show you the current color accents of the screen. 
For watching a movie, I'd recommend lower values to get an ambient lighting and smoother transitions. 
Higher saturation values than zero can be used to ignore the 256 shades of grey (from black to white) and will show you more saturated colors,
a higher brighness value ignores dark pixels and raises the overall brightness of the LEDs.
These combinated will lead to poppy colors and a more vibrant lighting.
The fading factor is something like the "aggressiveness". Higher fading factors will lead to a smoother transition between your captured colors. 
Just play around. 
The presets were optimized for colorful and brighter scenes, e.g. "Cat Quest 2"(video games), animes and working on the computer. 

I'd recommend no saturation (0) at all and a minimal brightness value (15) with a very high fading factor (210) to get a more natural lighting effect.
This works also well for documentaries and movies.

TODOs:

• Check the fading function for flaws
  • Write an extra gamma_correction() function.
  • Apply the gamma correction only while sending, not in retrieve_pixel().
• better USB-connection, e.g. detect disconnect and wait for re-connect
  • Resolved one issue: Can connect with any COM-port number below 1000
• Reinitialize enumerator and devices after device failure (could also fix the second issue)
• Implement modes
  • static light
  • standard light effects (rainbow, smooth, ...)
    • A fancy rainbow effect is the Arduino's default while the tool is not running.
  • overall darken/brighten factor
• Assign monitor areas to distinguished LEDs (Ambilight(TM)-style) (left and right side of the screen with overlap)
  • monitor iterations can be split in different loops(/threads)
  • re-write buffer-send
  • Arduino-script to distribute buffer-values to LEDs/stripes
• Turn the console application into a nice GUI after the bachelor's thesis.
  • Gamma-correction value shift and matched gamma-values for "night mode"

Appendix:

The project got compiled by Visual Studios' "Release Mode" with winSDK and only works on Windows 8.1 and higher (x64).
'lumos_maxima.cpp' is the Arduino code and got compiled to the arduino by the Arduino-IDE, using it's compiler (just press the "upload" button for CH340 after choosing the old boot loader)
..nothing fancy..

The TODOs will be implemented soon, when my current project is finished.

Known issues:

• A lot of programs and games handle the DirectX full screen switch well enough to work with this program. But the following happens sometimes:
  Switching from or to a fullscreen mode programm causes an access loss of the GPU-variables or it gets stuck in an windows-api-function. Restart the program and switch / 'Alt+Tab' back to the game within 5 seconds. This accounts to every display mode switch (change of resolution, lockscreen, changing games from window mode to fullscreen, ...).
• Netflix' desktop app and some other apps and sites with strong DRM-protection will block the win desktop duplication api from grabbing the frames. Workaround: use Firefox or whatever...

Porting it to Linux would require a replacement of the AcquireNextFrame()-function of the windows desktop duplication api and some other adjustments.
I'd suggest to grab the backbuffer of the GPU and load it in a <D3D11Texture2D> while using a directX-swap-chain.