improved color generation logic

src-ui/src/app/utils/color.ts

@@ -1,12 +1,48 @@
 
-  function componentToHex(c) {
-    var hex = c.toString(16);
-    return hex.length == 1 ? "0" + hex : hex;
+function componentToHex(c) {
+  var hex = Math.floor(c).toString(16)
+  return hex.length == 1 ? "0" + hex : hex
+}
+
+/**
+ * https://axonflux.com/handy-rgb-to-hsl-and-rgb-to-hsv-color-model-c
+ * 
+ * Converts an HSL color value to RGB. Conversion formula
+ * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
+ * Assumes h, s, and l are contained in the set [0, 1] and
+ * returns r, g, and b in the set [0, 255].
+ *
+ * @param   Number  h       The hue
+ * @param   Number  s       The saturation
+ * @param   Number  l       The lightness
+ * @return  Array           The RGB representation
+ */
+function hslToRgb(h, s, l){
+  var r, g, b
+
+  if(s == 0){
+      r = g = b = l // achromatic
+  }else{
+      function hue2rgb(p, q, t){
+          if(t < 0) t += 1
+          if(t > 1) t -= 1
+          if(t < 1/6) return p + (q - p) * 6 * t
+          if(t < 1/2) return q
+          if(t < 2/3) return p + (q - p) * (2/3 - t) * 6
+          return p
       }
 
-  export function randomColor() {
-    let r = Math.floor(Math.random() * 150) + 50
-    let g = Math.floor(Math.random() * 150) + 50
-    let b = Math.floor(Math.random() * 150) + 50
-    return `#${componentToHex(r)}${componentToHex(g)}${componentToHex(b)}`
+      var q = l < 0.5 ? l * (1 + s) : l + s - l * s
+      var p = 2 * l - q
+      r = hue2rgb(p, q, h + 1/3)
+      g = hue2rgb(p, q, h)
+      b = hue2rgb(p, q, h - 1/3)
   }
+
+  return [r * 255, g * 255, b * 255]
+}
+
+export function randomColor() {
+  let rgb = hslToRgb(Math.random(), 0.6, Math.random() * 0.4 + 0.4)
+  return `#${componentToHex(rgb[0])}${componentToHex(rgb[1])}${componentToHex(rgb[2])}`
+}