WMS

• transparent true plus format image png is required for overlays placed over a basemap.
• version 1.3.0 changes the axis order to latitude then longitude and uses the CRS parameter.
• setParams with noRedraw true defers the redraw until you explicitly request it.

var wms = L.tileLayer.wms('https://gis.example.com/geoserver/wms', {
  layers: 'city:roads,city:water',
  styles: '',
  format: 'image/png',
  transparent: true,
  version: '1.3.0',
  attribution: '© 城市地理信息中心',
  opacity: 0.8,
  maxZoom: 18
}).addTo(map);

/* 切换图层时不要重建，setParams 只改参数并重绘 */
document.getElementById('switch').addEventListener('click', function () {
  wms.setParams({ layers: 'city:buildings' }, true);
  wms.redraw();
});

/* 打印实际发出的 GetMap 地址，排查 400 时很有用 */
console.log(wms.getTileUrl({ x: 6745, y: 3104, z: 13 }));

• The default image jpeg fills blank areas with white and hides the basemap beneath.
• Some services return blank tiles at version 1.3.0, and falling back to 1.1.1 usually fixes it.