Add support for CSS color function notation to Led.RGB.color() (#1320)

* Add support for CSS functional notation to Led.RGB.color

Adds support for CSS functional notation (e.g. `"rgb(255, 255, 0)"`) to the `color()` method on the Led.RGB prototype.

Supports:

  - `rgb(r, g, b)`
  - `rgba(r, g, b, a)` where the alpha value in the range 0-1 modifies the color as an intensity function using `RGB.ToScaledRGB()`
  - `rgba(r, g, b)` and `rgb(r, g, b, a)` to comply with the [CSS Color Module Level 4 Draft](https://drafts.csswg.org/css-color/#rgb-functions)

* Add support for functional notation without commas

Also part of the CSS color level 4 spec.

* Fix lint errors

lib/led/rgb.js

@@ -311,6 +311,16 @@ RGB.ToRGB = function(red, green, blue) {
           green: parseInt(input.slice(2, 4), 16),
           blue: parseInt(input.slice(4, 6), 16)
         };
+      } else if (/^rgb/.test(input)) {
+        var args = input.match(/^rgba?\(([^)]+)\)$/)[1].split(/[\s,]+/);
+        update = {
+          red: parseInt(args[0], 10),
+          green: parseInt(args[1], 10),
+          blue: parseInt(args[2], 10)
+        };
+        if (args.length > 3) {
+          update = RGB.ToScaledRGB(100 * parseFloat(args[3]), update);
+        }
       } else {
         // color name
         return RGB.ToRGB(converter.keyword.rgb(input.toLowerCase()));

test/rgb.js

@@ -130,7 +130,7 @@ exports["RGB"] = {
   color: function(test) {
     var rgb = this.rgb;
 
-    test.expect(36);
+    test.expect(46);
 
     // returns this
     test.equal(this.rgb.color("#000000"), this.rgb);
@@ -229,6 +229,59 @@ exports["RGB"] = {
     }));
     this.write.reset();
 
+    // CSS functional notation
+    this.rgb.color("rgb(255, 100, 50)");
+    test.ok(this.write.calledOnce);
+    test.ok(this.write.calledWith({
+      red: 255,
+      green: 100,
+      blue: 50
+    }));
+    this.write.reset();
+
+    // CSS functional notation with alpha
+    // Subtle bug: Alpha is translated to intensity using linear scaling
+    // when it should probably use logarithmic scaling.
+    this.rgb.color("rgba(255, 100, 50, 0.5)");
+    test.ok(this.write.calledOnce);
+    test.ok(this.write.calledWith({
+      red: 128,
+      green: 50,
+      blue: 25
+    }));
+    this.write.reset();
+
+    // CSS4 functional notation (rgb and rgba become aliases)
+    this.rgb.color("rgba(255, 100, 50)");
+    test.ok(this.write.calledOnce);
+    test.ok(this.write.calledWith({
+      red: 255,
+      green: 100,
+      blue: 50
+    }));
+    this.write.reset();
+
+    // CSS4 functional notation with alpha (rgb and rgba become aliases)
+    // Also testing with no spaces to make sure that's supported.
+    this.rgb.color("rgb(255,100,50,0.5)");
+    test.ok(this.write.calledOnce);
+    test.ok(this.write.calledWith({
+      red: 128,
+      green: 50,
+      blue: 25
+    }));
+    this.write.reset();
+
+    // CSS4 functional notation without commas
+    this.rgb.color("rgb(255 100 50)");
+    test.ok(this.write.calledOnce);
+    test.ok(this.write.calledWith({
+      red: 255,
+      green: 100,
+      blue: 50
+    }));
+    this.write.reset();
+
     // bad values
     test.throws(function() {
       rgb.color(null);