我喜欢使用深色和浅色风格的 openlayers 贴图。那么如何更改地图颜色或地图样式呢? 我的朋友(亲爱的莫特扎)找到了我在这篇文章中回答的简单方法。 我的 html 文件是:
<!doctype html>
<html lang="en">
<head>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/css/ol.css" type="text/css">
<style>
.map {
height: 400px;
width: 50%;
}
</style>
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/build/ol.js"></script>
<title>OpenLayers example</title>
</head>
<body>
<h2>My Map</h2>
<div id="map" class="map"></div>
<script type="text/javascript">
var map = new ol.Map({
target: 'map',
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
view: new ol.View({
center: ol.proj.fromLonLat([37.41, 8.82]),
zoom: 4
})
});
// function applies greyscale to every pixel in canvas
</script>
</body>
</html>
openlayes 在
<canvas>
中显示地图。和 <canvas>
将添加到带有 openlayers 库的 <div>
容器中。因此,添加以下代码来添加地图并更改其颜色:
var map = new ol.Map({
target: 'map',//div with map id
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
view: new ol.View({
center: ol.proj.fromLonLat([61.2135, 28.2331]),
zoom: 13
})
});
//change map color
map.on('postcompose',function(e){
document.querySelector('canvas').style.filter="invert(90%)";
});
您还可以测试其他过滤器
const tile = new TileLayer({
source: new OSM()
});
tile.on('prerender', (evt) => {
// return
if (evt.context) {
const context = evt.context as CanvasRenderingContext2D;
context.filter = 'grayscale(80%) invert(100%) ';
context.globalCompositeOperation = 'source-over';
}
});
tile.on('postrender', (evt) => {
if (evt.context) {
const context = evt.context as CanvasRenderingContext2D;
context.filter = 'none';
}
});
在瓦片图层渲染前设置canvas滤镜,渲染后重置回无,这样后面的图层就不会受到任何影响,效果如下:
ol-ext 库允许您在 openlayers 图层上设置过滤器。它使用canvas合成操作来实现效果。
在线查看代码示例:https://viglino.github.io/ol-ext/examples/filter/map.filter.colorize.html