Newer, simpler luminance formula

noxxious · Jan 28, 2016 · bc1826d · bc1826d
1 parent c0385c4
commit bc1826d
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Showing 3 changed files with 56 additions and 41 deletions.
diff --git a/examples/luminance.js b/examples/luminance.js
@@ -8,44 +8,56 @@ orb.connect(function() {
   orb.color({ red: 255, green: 0, blue: 255 });
 
   setTimeout(function() {
-    console.log("color 1 - 50%");
-    // sets color to the provided hex value, at 50% luminance
-    orb.color(0xff0000, 50);
+    console.log("color 1 -50% luminance");
+    // sets color to the provided hex value, at -50% luminance
+    orb.color(0xcc0000, -0.5);
   }, 1000);
 
   setTimeout(function() {
-    console.log("color 1 - 100%");
-    // sets color to the same hex value, at 100% luminance
-    orb.color(0xff0000, 100);
+    console.log("color 1 normal% luminance");
+    // sets color to the same hex value, at +50% luminance
+    orb.color(0xcc0000, 0);
   }, 2000);
 
   setTimeout(function() {
-    console.log("color 2 - 33%");
-    // hex numbers can also be passed in strings
-    orb.color("00ff00", 33);
+    console.log("color 1 +50% luminance");
+    // sets color to the same hex value, at +50% luminance
+    orb.color(0xcc0000, 0.5);
   }, 3000);
 
   setTimeout(function() {
-    console.log("color 2 - 100%");
+    console.log("color 2 -50% luminance");
     // hex numbers can also be passed in strings
-    orb.color("00ff00", 100);
+    orb.color("00cc00", -0.5);
   }, 4000);
 
   setTimeout(function() {
-    console.log("color 3 - 75%");
-    // sets color to the provided color name
-    orb.color("magenta", 75);
+    console.log("color 2 normal% luminance");
+    // hex numbers can also be passed in strings
+    orb.color("00cc00", 0);
   }, 5000);
 
   setTimeout(function() {
-    console.log("color 3 - 0%");
-    // sets color to the provided color name
-    orb.color("magenta", 0);
+    console.log("color 2 +50% luminance");
+    // hex numbers can also be passed in strings
+    orb.color("00cc00", 0.5);
   }, 6000);
 
   setTimeout(function() {
-    console.log("color 3 - 100%");
+    console.log("color 3 -50% luminance");
     // sets color to the provided color name
-    orb.color("magenta", 100);
+    orb.color("magenta", -0.5);
   }, 7000);
+
+  setTimeout(function() {
+    console.log("color 3 normal% luminance");
+    // sets color to the provided color name
+    orb.color("magenta", 0);
+  }, 8000);
+
+  setTimeout(function() {
+    console.log("color 3 +50% luminance");
+    // sets color to the provided color name
+    orb.color("magenta", 0.5);
+  }, 9000);
 });
diff --git a/lib/devices/custom.js b/lib/devices/custom.js
@@ -26,27 +26,30 @@ function hexToRgb(num) {
 }
 
 /**
- * Converts a hex color number to RGB values,
- * adjusted by the relative luminance
+ * Converts a hex color number to luminance adjusted value
+ *
+ * @private
+ * @param {Object} hex hex color value to convert
+ * @param {Number} lum percentage of luminance
+ * @return {Object} converted color value
+ */
+function calculateLuminance(hex, lum) {
+  return Math.round(Math.min(Math.max(0, hex + (hex * lum)), 255));
+}
+
+/**
+ * Adjusts an RGB color by the relative luminance
  *
  * @private
  * @param {Object} rgb rgb color value to convert
  * @param {Number} lum percentage of luminance
  * @return {Object} RGB color values
  */
 function adjustLuminance(rgb, lum) {
-  var lp = lum / 100;
-
-  // calculate the full luminance
-  var yr = rgb.red * 0.33;
-  var yg = rgb.green * 0.5;
-  var yb = rgb.blue * 0.16;
-
-  // adjust to lum %
   var newRgb = {};
-  newRgb.red = Math.round(yr * lp / 0.33);
-  newRgb.green = Math.round(yg * lp / 0.5);
-  newRgb.blue = Math.round(yb * lp / 0.16);
+  newRgb.red = calculateLuminance(rgb.red, lum);
+  newRgb.green = calculateLuminance(rgb.green, lum);
+  newRgb.blue = calculateLuminance(rgb.blue, lum);
 
   return newRgb;
 }

diff --git a/spec/lib/devices/custom.spec.js b/spec/lib/devices/custom.spec.js
@@ -84,21 +84,21 @@ describe("Custom Device Functions", function() {
     });
 
     context("with luminance", function() {
-      it("converts to an RGB object at 50%", function() {
-        device.color(0xc3FF00, 50);
-        var color = { red: 98, blue: 0, green: 128 };
+      it("converts to an RGB object at +20%", function() {
+        device.color(0x6699cc, .2);
+        var color = { red: 0x7a, green: 0xb8, blue: 0xf5 };
         expect(rgb).to.be.calledWith(color);
       });
 
-      it("converts to an RGB object at 33%", function() {
-        device.color(0xc3FF00, 33);
-        var color = { red: 64, blue: 0, green: 84 };
+      it("converts to an RGB object at -50%", function() {
+        device.color(0x6699cc, -0.5);
+        var color = { red: 0x33, green: 0x4d, blue: 0x66 };
         expect(rgb).to.be.calledWith(color);
       });
 
-      it("converts to an RGB object at 100%", function() {
-        device.color(0xc3FF00, 100);
-        var color = { red: 195, blue: 0, green: 255 };
+      it("converts to an RGB object at normal %", function() {
+        device.color(0x6699cc, 0);
+        var color = { red: 0x66, green: 0x99, blue: 0xcc };
         expect(rgb).to.be.calledWith(color);
       });
     });