mapbox 经纬度刚好 zoom取整导致边角有部分无法加载
const bounds = window.map.getBounds()
var w = bounds._ne.lng- bounds._sw.lng;
var h = bounds._ne.lat- bounds._sw.lat;
const params = {
x1: bounds._sw.lng-w/4,
y1: bounds._sw.lat-h/4,
x2: bounds._ne.lng+w/4,
y2: bounds._ne.lat+h/4,
}
给边边角角的 经纬度 往外延伸