text color black/white based on bgcolor

by lid0

HTML

<div id="container"></div>

CSS

.a1 {
    width:200px;
    height:100px;
    display:inline-block;
    border:1px solid yellow;
    text-align:center;
    vertical-align:middle;
    
}

JavaScript

function rgbToHsl(r, g, b){
    r /= 255, g /= 255, b /= 255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, l = (max + min) / 2;

    if(max == min){
        h = s = 0; // achromatic
    }else{
        var d = max - min;
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
        switch(max){
            case r: h = (g - b) / d + (g < b ? 6 : 0); break;
            case g: h = (b - r) / d + 2; break;
            case b: h = (r - g) / d + 4; break;
        }
        h /= 6;
    }

    return [h, s, l]; 
}


 rgbcodes = ["#336699",
                "#e11d21",
                "#fbca04",
               ...