Openlayers示例18 | Draw Shapes(绘制形状)
这演示geometryFunction了ol/interaction/Draw. 从上面的下拉列表中选择一种形状类型以开始绘制。要激活手绘，请按住该Shift键。方形绘图是通过使用type: 'Circle'带有 a 的 type来实现的geometryFunction，它创建一个 4 边正多边形而不是圆形。箱形图type: 'Circle'与 a 一起使用，geometryFunction它创建一个箱形多边形而不是圆形。星形绘图使用自定义几何函数，该函数使用绘图交互提供的中心和半径将圆转换为星形。
<!DOCTYPE html>
<html lang="zn">
<head>
<meta charset="UTF-8">
<!-- 引入OpenLayers CSS样式 -->
<link rel="stylesheet"
href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.13.0/css/ol.css">
<!-- 引入OpenLayers JS库 -->
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.13.0/build/ol.js"></script>
<!-- css代码 -->
<style>
.map {
width: 100%;
height: 500px;
}
</style>
<title>Draw Shapes</title>
</head>
<body>
<div id="map" class="map"></div>
<form class="form-inline">
<label for="type">Shape type: </label>
<select class="form-control mr-2 mb-2 mt-2" id="type">
<option value="Circle">Circle</option>
<option value="Square">Square</option>
<option value="Box">Box</option>
<option value="Star">Star</option>
<option value="None">None</option>
</select>
<input class="form-control mr-2 mb-2 mt-2" type="button" value="Undo" id="undo">
</form>
</body>
<script>
const raster = new ol.layer.Tile({
source: new ol.source.OSM(),
});
const source = new ol.source.Vector({ wrapX: false });
const vector = new ol.layer.Vector({
source: source,
});
const map = new ol.Map({
layers: [raster, vector],
target: 'map',
view: new ol.View({
center: [-11000000, 4600000],
zoom: 4,
}),
});
const typeSelect = document.getElementById('type');
let draw; // global so we can remove it later
function addInteraction() {
let value = typeSelect.value;
if (value !== 'None') {
let 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';
geometryFunction = function (coordinates, geometry) {
const center = coordinates[0];
const last = coordinates[coordinates.length - 1];
const dx = center[0] - last[0];
const dy = center[1] - last[1];
const radius = Math.sqrt(dx * dx + dy * dy);
const rotation = Math.atan2(dy, dx);
const newCoordinates = [];
const numPoints = 12;
for (let i = 0; i < numPoints; ++i) {
const angle = rotation + (i * 2 * Math.PI) / numPoints;
const fraction = i % 2 === 0 ? 1 : 0.5;
const offsetX = radius * fraction * Math.cos(angle);
const offsetY = radius * fraction * Math.sin(angle);
newCoordinates.push([center[0] + offsetX, center[1] + offsetY]);
}
newCoordinates.push(newCoordinates[0].slice());
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);
}
}
/**
* Handle change event.
*/
typeSelect.onchange = function () {
map.removeInteraction(draw);
addInteraction();
};
document.getElementById('undo').addEventListener('click', function () {
draw.removeLastPoint();
});
addInteraction();
</script>
</html>
