Changing icon based on zoom level

Question

How do I go about changing an icon height & width based on the Google Maps zoom level?

I'm using Google Maps api v3.

Answer 1

This is the code I used eventually:

google.maps.event.addListener(google_map, 'zoom_changed', function() {
    var z = google_map.getZoom();

    _.each(map_shapes, function(s) {

        if (! $.isFunction(s.shape.getPosition)) return;

        var w = s.shape.getIcon().size.width;
        var h = s.shape.getIcon().size.height;

        s.shape.setIcon(new google.maps.MarkerImage(
            s.shape.getIcon().url, null, null, null, new google.maps.Size(
                w - Math.round(w / 3 * (last_zoom - z)),
                h - Math.round(h / 3 * (last_zoom - z)))
            )
        );

    });

    last_zoom = z;
});

Answer 2

You should be able to add a listener on the zoom change per the docs. It doesnt get passed anything, but you can get the property via the api.

google.maps.event.addListener(map, 'zoom_changed', function() {
    zoomLevel = map.getZoom();
    //this is where you will do your icon height and width change.     
  });

Answer 3

This code will change the size of the icon every time the zoom level changes so the icon is the same geographic size.

//create a marker image with the path to your graphic and the size of your graphic
var markerImage = new google.maps.MarkerImage(
    'myIcon.png',
    new google.maps.Size(8,8), //size
    null, //origin
    null, //anchor
    new google.maps.Size(8,8) //scale
);

var marker = new google.maps.Marker({
    position: new google.maps.LatLng(38, -98),
    map: map,
    icon: markerImage //set the markers icon to the MarkerImage
});

//when the map zoom changes, resize the icon based on the zoom level so the marker covers the same geographic area
google.maps.event.addListener(map, 'zoom_changed', function() {

    var pixelSizeAtZoom0 = 8; //the size of the icon at zoom level 0
    var maxPixelSize = 350; //restricts the maximum size of the icon, otherwise the browser will choke at higher zoom levels trying to scale an image to millions of pixels

    var zoom = map.getZoom();
    var relativePixelSize = Math.round(pixelSizeAtZoom0*Math.pow(2,zoom)); // use 2 to the power of current zoom to calculate relative pixel size.  Base of exponent is 2 because relative size should double every time you zoom in

    if(relativePixelSize > maxPixelSize) //restrict the maximum size of the icon
        relativePixelSize = maxPixelSize;

    //change the size of the icon
    marker.setIcon(
        new google.maps.MarkerImage(
            marker.getIcon().url, //marker's same icon graphic
            null,//size
            null,//origin
            null, //anchor
            new google.maps.Size(relativePixelSize, relativePixelSize) //changes the scale
        )
    );        
});