传单JS-外部控制

是否可以使用外部控件来缩放图像?我已经研究过文档,但是我找不到一个可能的解决方案。

HTML:

<div id="image-map"></div>

<button id="plus">+</button>
<button id="-">-</button>

JS:

var map = L.map('image-map', {
  minZoom: 1,
  maxZoom: 4,
  center: [0, 0],
  zoom: 1,
  crs: L.CRS.Simple
});

var w = 2000,
    h = 1500,
    url = 'http://kempe.net/images/newspaper-big.jpg';

var southWest = map.unproject([0, h], map.getMaxZoom()-1);
var northEast = map.unproject([w, 0], map.getMaxZoom()-1);
var bounds = new L.LatLngBounds(southWest, northEast);

L.imageOverlay(url, bounds).addTo(map);

map.setMaxBounds(bounds);
map.scrollWheelZoom.disable();

JSFIDDLE: http://jsfiddle.net/u51pgv4h/2/