For a side project, I needed a way to determine, whether to use a dark font or light font, based on the background-color, which is configurable by the user. After googling for a while, I found a perfect solution (for my use case at least).
If luminance of background-color is less than 0.5, use light font else use dark font. Luminance of a given RGB value can be calculated using the following function:
/**
* red number HEX value between 0 and 255 scaled to 0 and 1
* green number HEX value between 0 and 255 scaled to 0 and 1
* blue number HEX value between 0 and 255 scaled to 0 and 1
*/
function getLuminance(red, green, blue) {
const luminance = 1 - (0.299 * red + 0.587 * green + 0.114 * blue);
return luminance;
}This utility function is also available as a part of Polished library, and can handle hex values too. Will Bamford has a CodePen demonstrating the same.