react-native-side-reveal-menu/src/utils/colorUtils.js

Animated menu component for React Native.

//solution taken from accepted answer of this stack overflow question
//http://stackoverflow.com/questions/5560248/programmatically-lighten-or-darken-a-hex-color-or-rgb-and-blend-colors

export const shadeColor = (col, amt) => {
   var usePound = false;
   if (col[0] == "#") {
      col = col.slice(1);
      usePound = true;
   }

   var num = parseInt(col, 16);

   var r = (num >> 16) + amt;

   if (r > 255) r = 255;
   else if (r < 0) r = 0;

   var b = ((num >> 8) & 0x00FF) + amt;

   if (b > 255) b = 255;
   else if (b < 0) b = 0;

   var g = (num & 0x0000FF) + amt;

   if (g > 255) g = 255;
   else if (g < 0) g = 0;

   return (usePound ? "#" : "") + (g | (b << 8) | (r << 16)).toString(16);
}