原文链接及内容
这里演示了ol/interaction/Draw绘制交互的geometryFunction选项的使用。从下拉菜单中选择一个几何形状类型开始绘制。要激活徒手绘图，请在绘制时按住Shift键。正方形绘图是通过使用type: 'Circle'类型和一个geometryFunction来实现的，该函数会创建一个存在4条边的正多边形而不是一个圆。(方)框绘制也是使用type: 'Circle'和一个geometryFunction来实现的，该函数创建一个盒子形状的多边形而不是一个圆。同样地，绘制星星依旧使用了自定义几何函数，该函数使用绘制交互提供的中心和半径将圆形转换为星星形状。
main.js代码如下：
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| import Draw, {
createBox,
createRegularPolygon,
} from 'ol/interaction/Draw.js';
import Map from 'ol/Map.js';
import Polygon from 'ol/geom/Polygon.js';
import View from 'ol/View.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';
const raster = new TileLayer({
source: new OSM(),
});
const source = new VectorSource({wrapX: false});
const vector = new VectorLayer({
source: source,
});
const map = new Map({
layers: [raster, vector],
target: 'map',
view: new View({
center: [-11000000, 4600000],
zoom: 4,
}),
});
const typeSelect = document.getElementById('type');
let draw;
function addInteraction() {
let value = typeSelect.value;
if (value !== 'None') {
let geometryFunction;
if (value === 'Square') {
value = 'Circle';
geometryFunction = createRegularPolygon(4);
} else if (value === 'Box') {
value = 'Circle';
geometryFunction = 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 Polygon([newCoordinates]);
} else {
geometry.setCoordinates([newCoordinates]);
}
return geometry;
};
}
draw = new Draw({
source: source,
type: value,
geometryFunction: geometryFunction,
});
map.addInteraction(draw);
}
}
typeSelect.onchange = function () {
map.removeInteraction(draw);
addInteraction();
};
document.getElementById('undo').addEventListener('click', function () {
draw.removeLastPoint();
});
addInteraction();
|
界面布局文件index.html代码如下：
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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Draw Shapes</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/css/bootstrap.min.css">
<link rel="stylesheet" href="node_modules/ol/ol.css">
<style>
.map {
width: 100%;
height: 400px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<div class="row">
<div class="col-auto">
<span class="input-group">
<label class="input-group-text" for="type">Shape type:</label>
<select class="form-select" 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" type="button" value="Undo" id="undo">
</span>
</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
<script type="module" src="main.js"></script>
</body>
</html>
|
)
