HTML Color Names (Relative Lightness, linear color space) by denisemauldin

index.html

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <style>
    body { 
      margin:0;position:fixed;top:0;right:0;bottom:0;left:0;
      padding: 10px;
    }    
    section {
      clear: both;
    }
    .color {
      float: left;
      padding: 3px 5px;
      margin: 2px 5px;
      font-family: Helvetica;
      border-radius: 3px
    }
  </style>
</head>

<body>
  <label>Threshold: <input type="range" min="0" max="1" value="0.5" step="0.01" oninput="redraw(this.value)"></label>
  <section></section>
  
  <script>
    function gammaToLinear(x) {
        x /= 255;
        if (x <= 0.03928) {
    	    return x / 12.92;
  	  	} else {
       		return ((x + 0.055) / 1.055)**2.4;
	  	  }		
   	 }	

    function redraw(threshold) {
      console.log(threshold)
		   cdivs.style({
        "background-color": function(d) { return d.color },
        color: function(d) {
          var rgb = d3.rgb(d.color);
          
          var L2 = 0.2126 * gammaToLinear(rgb.r) + 0.7152 * gammaToLinear(rgb.g) + 0.0722 * gammaToLinear(rgb.b)    
          if(L2 >= threshold) {
            return "black"
          } else {
            return "white"
          }
        }
      })
    }
    
		var display = d3.select("section");
    var cdivs;
    d3.csv("colors.csv", function(err, colors) {
      cdivs = display.selectAll("div.color")
      	.data(colors)
      cdivs.enter()
      	.append("div").classed("color", true);
      
      cdivs.text(function(d) { 
        return d.color.toLowerCase()
      });
      
      redraw(0.5);
    })
  </script>
</body>