<!DOCTYPE html> <html> <head> <title>Layer Clipping</title> <link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css"> <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x --> <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script> <script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script> <style> #map { background: transparent; } </style> </head> <body> <div id="map" class="map"></div> <script> var osm = new ol.layer.Tile({ source: new ol.source.OSM() }); var map = new ol.Map({ layers: [osm], target: 'map', controls: ol.control.defaults({ attributionOptions: /** @type {olx.control.AttributionOptions} */ ({ collapsible: false }) }), view: new ol.View({ center: [0, 0], zoom: 2 }) }); osm.on('precompose', function(event) { var ctx = event.context; ctx.save(); var pixelRatio = event.frameState.pixelRatio; var size = map.getSize(); ctx.translate(size[0] / 2 * pixelRatio, size[1] / 2 * pixelRatio); ctx.scale(3 * pixelRatio, 3 * pixelRatio); ctx.translate(-75, -80); ctx.beginPath(); ctx.moveTo(75, 40); ctx.bezierCurveTo(75, 37, 70, 25, 50, 25); ctx.bezierCurveTo(20, 25, 20, 62.5, 20, 62.5); ctx.bezierCurveTo(20, 80, 40, 102, 75, 120); ctx.bezierCurveTo(110, 102, 130, 80, 130, 62.5); ctx.bezierCurveTo(130, 62.5, 130, 25, 100, 25); ctx.bezierCurveTo(85, 25, 75, 37, 75, 40); ctx.clip(); ctx.translate(75, 80); ctx.scale(1 / 3 / pixelRatio, 1 / 3 / pixelRatio); ctx.translate(-size[0] / 2 * pixelRatio, -size[1] / 2 * pixelRatio); }); osm.on('postcompose', function(event) { var ctx = event.context; ctx.restore(); }); </script> </body> </html>
OpenLayers示例代码:图层剪切
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