我目前正在使用leaflet和canvas在leaflet地图上绘制一系列线条。然而,我无法使用canvas在这些线条上绘制箭头。我找到了像polyline decorator这样的项目,但它非常慢,而且我只想在指定的缩放距离(>=13)下显示箭头。请问该如何使用leaflet实现这一点呢?我不需要重复的箭头,只需要一种显示线条方向的方法。谢谢。
我知道这个答案有点晚,但它可以有很好的性能,并且不需要任何插件。
您可以将图标(当前为三角箭头(▶))更改为任何您想要的东西,其初始方向应指向右侧(零度角)。
您还可以更改要显示的箭头数量(在此示例中为5)
CSS 代码:
.arrow-icon {
width: 14px;
height: 14px;
}
.arrow-icon > div {
margin-left: -1px;
margin-top: -3px;
transform-origin: center center;
font: 12px/1.5 "Helvetica Neue", Arial, Helvetica, sans-serif;
}
这里是Javascript代码。 getArrows
函数接受折线坐标的数组(以及可选参数颜色和每条线上箭头数量),并返回标记数组(只需复制并粘贴所有内容):
function getArrows(arrLatlngs, color, arrowCount, mapObj) {
if (typeof arrLatlngs === undefined || arrLatlngs == null ||
(!arrLatlngs.length) || arrLatlngs.length < 2)
return [];
if (typeof arrowCount === 'undefined' || arrowCount == null)
arrowCount = 1;
if (typeof color === 'undefined' || color == null)
color = '';
else
color = 'color:' + color;
var result = [];
for (var i = 1; i < arrLatlngs.length; i++) {
var icon = L.divIcon({ className: 'arrow-icon', bgPos: [5, 5], html: '<div style="' + color + ';transform: rotate(' + getAngle(arrLatlngs[i - 1], arrLatlngs[i], -1).toString() + 'deg)">▶</div>' });
for (var c = 1; c <= arrowCount; c++) {
result.push(L.marker(myMidPoint(arrLatlngs[i], arrLatlngs[i - 1], (c / (arrowCount + 1)), mapObj), { icon: icon }));
}
}
return result;
}
function getAngle(latLng1, latlng2, coef) {
var dy = latlng2[0] - latLng1[0];
var dx = Math.cos(Math.PI / 180 * latLng1[0]) * (latlng2[1] - latLng1[1]);
var ang = ((Math.atan2(dy, dx) / Math.PI) * 180 * coef);
return (ang).toFixed(2);
}
function myMidPoint(latlng1, latlng2, per, mapObj) {
if (!mapObj)
throw new Error('map is not defined');
var halfDist, segDist, dist, p1, p2, ratio,
points = [];
p1 = mapObj.project(new L.latLng(latlng1));
p2 = mapObj.project(new L.latLng(latlng2));
halfDist = distanceTo(p1, p2) * per;
if (halfDist === 0)
return mapObj.unproject(p1);
dist = distanceTo(p1, p2);
if (dist > halfDist) {
ratio = (dist - halfDist) / dist;
var res = mapObj.unproject(new Point(p2.x - ratio * (p2.x - p1.x), p2.y - ratio * (p2.y - p1.y)));
return [res.lat, res.lng];
}
}
function distanceTo(p1, p2) {
var x = p2.x - p1.x,
y = p2.y - p1.y;
return Math.sqrt(x * x + y * y);
}
function toPoint(x, y, round) {
if (x instanceof Point) {
return x;
}
if (isArray(x)) {
return new Point(x[0], x[1]);
}
if (x === undefined || x === null) {
return x;
}
if (typeof x === 'object' && 'x' in x && 'y' in x) {
return new Point(x.x, x.y);
}
return new Point(x, y, round);
}
function Point(x, y, round) {
this.x = (round ? Math.round(x) : x);
this.y = (round ? Math.round(y) : y);
}
然后只需绘制leaflet折线(仅适用于latLng
坐标数组而不是坐标数组的数组):
// array of coordinates
var mylatlngs = [
[55.555, 33.33],
[..., ...],
[..., ...],
[..., ...],
[..., ...],
...
];
var polyline = L.polyline(mylatlngs, { color: 'red' }).addTo(map);
// draw 5 arrows per line
L.featureGroup(getArrows(mylatlngs, 'red', 5,map)).addTo(map);