add color palette

components/style/color/color-palette.js

@@ -0,0 +1,72 @@
+const tinyColor = require('./tiny-color');
+
+module.exports = {
+  install: function(less, pluginManager, functions) {
+    functions.add('color-palette', function(arg1, arg2) {
+      const color = arg1.value;
+      const index = arg2.value;
+
+      var hueStep = 2;
+      var saturationStep = 16;
+      var saturationStep2 = 5;
+      var brightnessStep1 = 5;
+      var brightnessStep2 = 15;
+      var lightColorCount = 5;
+      var darkColorCount = 4;
+
+      var getHue = function(hsv, i, isLight) {
+        var hue;
+        if (hsv.h >= 60 && hsv.h <= 240) {
+          hue = isLight ? hsv.h - hueStep * i : hsv.h + hueStep * i;
+        } else {
+          hue = isLight ? hsv.h + hueStep * i : hsv.h - hueStep * i;
+        }
+        if (hue < 0) {
+          hue += 360;
+        } else if (hue >= 360) {
+          hue -= 360;
+        }
+        return Math.round(hue);
+      };
+
+      var getSaturation = function(hsv, i, isLight) {
+        var saturation;
+        if (isLight) {
+          saturation = Math.round(hsv.s * 100) - saturationStep * i;
+        } else if (i == darkColorCount) {
+          saturation = Math.round(hsv.s * 100) + saturationStep;
+        } else {
+          saturation = Math.round(hsv.s * 100) + saturationStep2 * i;
+        }
+        if (saturation > 100) {
+          saturation = 100;
+        }
+        if (isLight && i === lightColorCount && saturation > 10) {
+          saturation = 10;
+        }
+        if (saturation < 6) {
+          saturation = 6;
+        }
+        return Math.round(saturation);
+      };
+      var getValue = function(hsv, i, isLight) {
+        if (isLight) {
+          return Math.round(hsv.v * 100) + brightnessStep1 * i;
+        }
+        return Math.round(hsv.v * 100) - brightnessStep2 * i;
+      };
+
+      // Calculation
+      return (function() {
+        var isLight = index <= 6;
+        var hsv = tinyColor(color).toHsv();
+        var i = isLight ? lightColorCount + 1 - index : index - lightColorCount - 1;
+        return tinyColor({
+          h: getHue(hsv, i, isLight),
+          s: getSaturation(hsv, i, isLight),
+          v: getValue(hsv, i, isLight),
+        }).toHexString();
+      })();
+    });
+  },
+};