Canvas pointer coords no matter where and how big canvas is

canvascoords.js

relMouseCoords: function(canvas, e) 
{
    var rect = canvas.getBoundingClientRect();
    var x = e.clientX - rect.left;
    var y = e.clientY - rect.top;
    return { x: x, y: y };
}

relTapCoords: function(canvas, e) 
{
    var rect = canvas.getBoundingClientRect();
    var x = e.touches[0].clientX - rect.left;
    var y = e.touches[0].clientY - rect.top;
    return { x: x, y: y };
}