New colour generator

core/js/placeholder.js

 /**
  * ownCloud
  *
+ * @author John Molakvoæ
+ * @copyright 2016 John Molakvoæ <fremulon@protonmail.com>
  * @author Morris Jobke
  * @copyright 2013 Morris Jobke <morris.jobke@gmail.com>
  *
@@ -48,16 +50,64 @@
 
 (function ($) {
 	$.fn.imageplaceholder = function(seed, text, size) {
-		// set optional argument "text" to value of "seed" if undefined
 		text = text || seed;
 
-		var hash = md5(seed).substring(0, 4),
-			maxRange = parseInt('ffff', 16),
-			hue = parseInt(hash, 16) / maxRange * 256,
-			height = this.height() || size || 32;
-		this.css('background-color', 'hsl(' + hue + ', 90%, 65%)');
+		var hash = seed.toLowerCase().replace(/[^0-9a-f]+/g, '');
+
+		// Already a md5 hash?
+		if( !hash.match(/^[0-9a-f]{32}$/g) ) {
+			hash = md5(hash);
+		}
+
+		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];
+		}
+
+		// Init vars
+		var result = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
+		var rgb = [0, 0, 0];
+		var sat = 80;
+		var lum = 68;
+		var modulo = 16;
+
+		// Splitting evenly the string
+		for(var i in hash) {
+			result[i%modulo] = result[i%modulo] + parseInt(hash.charAt(i), 16).toString();
+		}
+
+		// Converting our data into a usable rgb format
+		// Start at 1 because 16%3=1 but 15%3=0 and makes the repartition even
+		for(var count=1;count<modulo;count++) {
+			rgb[count%3] += parseInt(result[count]);
+		}
+		var hsl = rgbToHsl(rgb[0], rgb[1], rgb[2]);
+
+		// Classic formulla to check the brigtness for our eye
+		// If too bright, lower the sat
+		var bright = Math.sqrt( 0.299 * Math.pow(rgb[0], 2) + 0.587 * Math.pow(rgb[1], 2) + 0.114 * Math.pow(rgb[2], 2) );
+		if (bright >= 200) {
+			sat = 60;
+		}
+		var hue = parseInt(hsl[0] * 360);
+		this.css('background-color', 'hsl('+hue+', '+sat+'%, '+lum+'%)');
 
 		// Placeholders are square
+		var height = this.height() || size || 32;
 		this.height(height);
 		this.width(height);