MOB-2275 Calculate background color for map tiles' sets

How about using array instead of object? My guess is that this will decrease the memory usage and you already have the indexes defined as sequential numbers so you can use them as indexes of the array like: [chanelIdxRed, chanelIdxBlue, chanelIdxBlue, chanelIdxAlpha]
And to get the values something like:
```
var channels = {
	chanelIdxRed: 0,
	chanelIdxGreen: 1,
	chanelIdxBlue: 2,
	chanelIdxAlpha: 3,
};

function getColorObject(x, y, pixels) {
  var result = [],
    channel;
  Object.keys(channels).forEach(function (key) {
    channel = channels[key];
    result[channel] = pixels.get(y, x, channel);
  }
  return result;
}
```