google maps circle to polyline coordinate array

问题:

how to get array of polyline coordinates from google.maps.Circle's object

there is no api doc entry about that

回答1:

A google.maps.Circle doesn't contain an array of coordinates. If you want a google.maps.Polygon that is shaped like a circle, you need to make one.

function drawCircle(point, radius, dir) { 
  var d2r = Math.PI / 180;   // degrees to radians 
  var r2d = 180 / Math.PI;   // radians to degrees 
  var earthsradius = 3963; // 3963 is the radius of the earth in miles

  var points = 32; 

  // find the raidus in lat/lon 
  var rlat = (radius / earthsradius) * r2d; 
  var rlng = rlat / Math.cos(point.lat() * d2r); 

  var extp = new Array(); 
  if (dir==1) {
     var start=0;
     var end=points+1; // one extra here makes sure we connect the path
  } else {
     var start=points+1;
     var end=0;
  }
  for (var i=start; (dir==1 ? i < end : i > end); i=i+dir)  
  { 
     var theta = Math.PI * (i / (points/2)); 
     ey = point.lng() + (rlng * Math.cos(theta)); // center a + radius x * cos(theta) 
     ex = point.lat() + (rlat * Math.sin(theta)); // center b + radius y * sin(theta) 
     extp.push(new google.maps.LatLng(ex, ey)); 
  } 
  return extp;
}

var circle = new google.maps.Polygon({
               map: map,
               paths: [drawCircle(new google.maps.LatLng(-33.9,151.2), 100, 1)],
               strokeColor: "#0000FF",
               strokeOpacity: 0.8,
               strokeWeight: 2,
               fillColor: "#FF0000",
               fillOpacity: 0.35
});

Example