Overlapping Vector Shapes Measurement

I have a piece from an existing Script we have used in the past that think could be a good jumping off point
The original script was written by @adamdehaven 

// Spec object
  // ===========================
  function specSingle(bound, where) {

    // width and height
    var w = bound[2] - bound[0];

    // a & b are the horizontal or vertical positions that change
    // c is the horizontal or vertical position that doesn't change
    var a = bound[0];
    var b = bound[2];
    var c = bound[1];

    // xy='x' (horizontal measurement), xy='y' (vertical measurement)
    var xy = "x";

    // a direction flag for placing the measurement lines.
    var dir = 1;

    switch (where) {
      case "Top":
        a = bound[0];
        b = bound[2];
        c = bound[1];
        xy = "x";
        dir = 1;
        break;
    }
  }