本文基于腾讯课堂老胡的课《跟我学Openlayers--基础实例详解》做的学习笔记，使用的openlayers 5.3.x api。
源码 见 1051.html ，对应的 官网示例 https://openlayers.org/en/latest/examples/draw-shapes.html
关键是addInteraction函数的实现
ol.interaction.Draw.createRegularPolygon
ol.interaction.Draw.createBox
image.png
image.png
<!DOCTYPE html>
<html>
<head>
<title>绘制形状</title>
<link rel="stylesheet" href="../include/ol.css" type="text/css" />
<script src="../include/ol.js"></script>
</head>
<style></style>
<body>
<form class="form-inline">
<label>形状类型 </label>
<select id="type">
<option value="Circle">圆形</option>
<option value="Square">方形</option>
<option value="Box">矩形</option>
<option value="Star">六角星型</option>
<option value="None">无</option>
</select>
</form>
<div id="map" class="map"></div>
<script>
var raster = new ol.layer.Tile({
source: new ol.source.OSM()
});
var source = new ol.source.Vector({
wrapX: false
});
var vector = new ol.layer.Vector({
source: source
});
var map = new ol.Map({
layers: [raster, vector],
target: 'map',
view: new ol.View({
center: [-11000000, 4600000],
zoom: 4
})
});
var typeSelect = document.getElementById('type');
var draw;
function addInteraction() {
var value = typeSelect.value;
if (value !== 'None') {
var geometryFunction;
if (value === 'Square') {
value = 'Circle';
geometryFunction = ol.interaction.Draw.createRegularPolygon(4);
} else if (value === 'Box') {
value = 'Circle';
geometryFunction = ol.interaction.Draw.createBox();
} else if (value === 'Star') {
value = 'Circle';
//自定义绘图函数，绘制六角星，共12个顶点
geometryFunction = function (coordinates, geometry) {
//中心点
var center = coordinates[0];
//鼠标点击的另一个点
var last = coordinates[1];
var dx = center[0] - last[0];
var dy = center[1] - last[1];
//半径
var radius = Math.sqrt(dx * dx + dy * dy);
//反正切函数，计算旋转的角度
var rotation = Math.atan2(dy, dx);
//用来记录顶点坐标的数组
var newCoordinates = [];
//顶点个数
var numPoints = 12;
for (var i = 0; i < numPoints; ++i) {
//顶点相对转过的角度
var angle = rotation + i * 2 * Math.PI / numPoints;
//确定凸顶点和凹顶点
var fraction = i % 2 === 0 ? 1 : 0.58;
//计算顶点的坐标
var offsetX = radius * fraction * Math.cos(angle);
var offsetY = radius * fraction * Math.sin(angle);
newCoordinates.push([center[0] + offsetX, center[1] + offsetY]);
}
newCoordinates.push(newCoordinates[0].slice()); //把第一个顶点坐标加入，形成一个闭合的环
if (!geometry) {
geometry = new ol.geom.Polygon([newCoordinates]);
} else {
geometry.setCoordinates([newCoordinates]);
}
return geometry;
};
}
draw = new ol.interaction.Draw({
source: source,
type: value,
geometryFunction: geometryFunction
});
map.addInteraction(draw);
}
}
typeSelect.onchange = function () {
map.removeInteraction(draw);
addInteraction();
};
addInteraction();
</script>
</body>
</html>
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