Get a suitable colour for an overlay style map - based on the length of your data.
You can add any CSS named colour (e.g.
cyan... etc.) or HEX colour as the second parameter (e.g.
Simply pass the Array/Object you want to use, along with the colour - and retrieve a suitable RGBA colour for the background of your hashmap based on the size.
var map = new Array(10); var colour = new HeatMapColour(map, 'red').rgba; // => rgba(255,0,0,0.45)