BDSM.js extracts dominant colors from the top and the bottom areas of an image.
npm install bdsm@0.2.2 --save
var bdsm = require('bdsm');
bdsm.findDominantColors('image.jpg').then(function (colors) {
console.log(colors);
});
will give you something like
{ top: { r: 151, g: 189, b: 212 },
bottom: { r: 188, g: 163, b: 147 } }
BDSM.js uses ImageMagick and runs on Node.
It is tested with IM 6.8.7 but other versions may work as well.