Seems very useful, thanks. Curious how it affects cpu usage. Would be cool if you can explain how it works. I can see even the gifs and videos(which I think makes this even more useful) are rendered black & white.
Potentially there's power savings on a mobile device by restricting the color palette to grayscale?
If so this could be incorporated into one's phone's battery saver mode.
Yep, you got it. For the most part I'm just adding filter: grayscale(100%) to the html element.
There some other stuff going on though. I noticed that for the html and body elements, if they had a background image/color, the grayscale trick wouldn't work for them.
So, on the options page I added a toggle to "Remove All Background Colors and Images No Matter What". This goes through the page and checks if there is a background image or color, then uses this library (https://github.com/bgrins/TinyColor) to check the perceived lightness of the color and changes the background to use a shade of gray instead.
Performance wise, I don't have any specific numbers, but I did a lot of dogfooding on my own before releasing and didn't notice any perceivable slowdown.