# 三.extent

# 1.动态集群

查看代码详情
<template>
  <div ref="map" class="map"></div>
</template>

<script>
export default {
  mounted() {
    let {
      Feature,
      format: { GeoJSON },
      geom: { LineString, Point, Polygon },
      Map,
      View,
      layer: { Tile: TileLayer, Vector: VectorLayer },
      source: { XYZ, Cluster, Vector: VectorSource },
      style: { Circle: CircleStyle, Fill, Icon, Stroke, Style, Text },
      proj: { fromLonLat },
      extent: { createEmpty, extend, getWidth },
    } = ol
    const circleDistanceMultiplier = 1
    const circleFootSeparation = 28
    const circleStartAngle = Math.PI / 2

    const convexHullFill = new Fill({
      color: "rgba(255, 153, 0, 0.4)",
    })
    const convexHullStroke = new Stroke({
      color: "rgba(204, 85, 0, 1)",
      width: 1.5,
    })
    const outerCircleFill = new Fill({
      color: "rgba(255, 153, 102, 0.3)",
    })
    const innerCircleFill = new Fill({
      color: "rgba(255, 165, 0, 0.7)",
    })
    const textFill = new Fill({
      color: "#fff",
    })
    const textStroke = new Stroke({
      color: "rgba(0, 0, 0, 0.6)",
      width: 3,
    })
    const innerCircle = new CircleStyle({
      radius: 14,
      fill: innerCircleFill,
    })
    const outerCircle = new CircleStyle({
      radius: 20,
      fill: outerCircleFill,
    })
    const darkIcon = new Icon({
      src: this.$withBase("/data/icons/emoticon-cool.svg"),
    })
    const lightIcon = new Icon({
      src: this.$withBase("/data/icons/emoticon-cool-outline.svg"),
    })
    function clusterMemberStyle(clusterMember) {
      return new Style({
        geometry: clusterMember.getGeometry(),
        image: clusterMember.get("LEISTUNG") > 5 ? darkIcon : lightIcon,
      })
    }
    let clickFeature, clickResolution
    function clusterCircleStyle(cluster, resolution) {
      if (cluster !== clickFeature || resolution !== clickResolution) {
        return
      }
      const clusterMembers = cluster.get("features")
      const centerCoordinates = cluster.getGeometry().getCoordinates()
      return generatePointsCircle(
        clusterMembers.length,
        cluster.getGeometry().getCoordinates(),
        resolution
      ).reduce((styles, coordinates, i) => {
        const point = new Point(coordinates)
        const line = new LineString([centerCoordinates, coordinates])
        styles.unshift(
          new Style({
            geometry: line,
            stroke: convexHullStroke,
          })
        )
        styles.push(
          clusterMemberStyle(
            new Feature({
              ...clusterMembers[i].getProperties(),
              geometry: point,
            })
          )
        )
        return styles
      }, [])
    }
    function generatePointsCircle(count, clusterCenter, resolution) {
      const circumference =
        circleDistanceMultiplier * circleFootSeparation * (2 + count)
      let legLength = circumference / (Math.PI * 2)
      const angleStep = (Math.PI * 2) / count
      const res = []
      let angle
      legLength = Math.max(legLength, 35) * resolution
      for (let i = 0; i < count; ++i) {
        angle = circleStartAngle + i * angleStep
        res.push([
          clusterCenter[0] + legLength * Math.cos(angle),
          clusterCenter[1] + legLength * Math.sin(angle),
        ])
      }

      return res
    }
    let hoverFeature
    function clusterHullStyle(cluster) {
      if (cluster !== hoverFeature) {
        return
      }
      const originalFeatures = cluster.get("features")
      const points = originalFeatures.map((feature) =>
        feature.getGeometry().getCoordinates()
      )
      return new Style({
        geometry: new Polygon([monotoneChainConvexHull(points)]),
        fill: convexHullFill,
        stroke: convexHullStroke,
      })
    }
    function clusterStyle(feature) {
      const size = feature.get("features").length
      if (size > 1) {
        return [
          new Style({
            image: outerCircle,
          }),
          new Style({
            image: innerCircle,
            text: new Text({
              text: size.toString(),
              fill: textFill,
              stroke: textStroke,
            }),
          }),
        ]
      } else {
        const originalFeature = feature.get("features")[0]
        return clusterMemberStyle(originalFeature)
      }
    }
    const vectorSource = new VectorSource({
      format: new GeoJSON(),
      url: this.$withBase("/data/geojson/photovoltaic.json"),
    })
    const clusterSource = new Cluster({
      attributions:
        'Data: <a href="https://www.data.gv.at/auftritte/?organisation=stadt-wien">Stadt Wien</a>',
      distance: 35,
      source: vectorSource,
    })
    const clusterHulls = new VectorLayer({
      source: clusterSource,
      style: clusterHullStyle,
    })
    const clusters = new VectorLayer({
      source: clusterSource,
      style: clusterStyle,
    })
    const clusterCircles = new VectorLayer({
      source: clusterSource,
      style: clusterCircleStyle,
    })
    const raster = new TileLayer({
      source: new XYZ({
        attributions:
          'Base map: <a target="_blank" href="https://basemap.at/">basemap.at</a>',
        url: "https://maps{1-4}.wien.gv.at/basemap/bmapgrau/normal/google3857/{z}/{y}/{x}.png",
      }),
    })
    const map = new Map({
      layers: [raster, clusterHulls, clusters, clusterCircles],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
        maxZoom: 19,
        extent: [
          ...fromLonLat([16.1793, 48.1124]),
          ...fromLonLat([16.5559, 48.313]),
        ],
        showFullExtent: true,
      }),
    })
    map.on("pointermove", (event) => {
      clusters.getFeatures(event.pixel).then((features) => {
        if (features[0] !== hoverFeature) {
          hoverFeature = features[0]
          clusterHulls.setStyle(clusterHullStyle)
          map.getTargetElement().style.cursor =
            hoverFeature && hoverFeature.get("features").length > 1
              ? "pointer"
              : ""
        }
      })
    })
    map.on("click", (event) => {
      clusters.getFeatures(event.pixel).then((features) => {
        if (features.length > 0) {
          const clusterMembers = features[0].get("features")
          if (clusterMembers.length > 1) {
            const extent = createEmpty()
            clusterMembers.forEach((feature) =>
              extend(extent, feature.getGeometry().getExtent())
            )
            const view = map.getView()
            const resolution = map.getView().getResolution()
            if (
              view.getZoom() === view.getMaxZoom() ||
              (getWidth(extent) < resolution && getWidth(extent) < resolution)
            ) {
              clickFeature = features[0]
              clickResolution = resolution
              clusterCircles.setStyle(clusterCircleStyle)
            } else {
              view.fit(extent, { duration: 500, padding: [50, 50, 50, 50] })
            }
          }
        }
      })
    })
  },
}
</script>
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# 2.集群功能

查看代码详情
<template>
  <div>
    <div ref="map" class="map"></div>
    <form>
      <div class="form-group">
        <label for="distance" class="col-form-label">集群距离</label>
        <input
          id="distance"
          class="form-control-range"
          type="range"
          min="0"
          max="200"
          step="1"
          value="40"
        />
        <small class="form-text text-muted"> 要素聚集在一起的距离 </small>
      </div>
      <div class="form-group">
        <label for="min-distance" class="col-form-label">最小距离</label>
        <input
          id="min-distance"
          class="form-control-range"
          type="range"
          min="0"
          max="200"
          step="1"
          value="20"
        />
        <small class="form-text text-muted">
          簇之间的最小距离。不能大于配置的距离。
        </small>
      </div>
    </form>
  </div>
</template>

<script>
export default {
  mounted() {
    let {
      Feature,
      Map,
      geom: { Point },
      extent: { boundingExtent },
      View,
      layer: { Tile: TileLayer, Vector: VectorLayer },
      source: { Cluster, OSM, Vector: VectorSource },
      style: { Circle: CircleStyle, Fill, Stroke, Style, Text },
    } = ol
    const distanceInput = document.getElementById("distance")
    const minDistanceInput = document.getElementById("min-distance")

    const count = 20000
    const features = new Array(count)
    const e = 4500000
    for (let i = 0; i < count; ++i) {
      const coordinates = [2 * e * Math.random() - e, 2 * e * Math.random() - e]
      features[i] = new Feature(new Point(coordinates))
    }
    const source = new VectorSource({
      features: features,
    })

    const clusterSource = new Cluster({
      distance: parseInt(distanceInput.value, 10),
      minDistance: parseInt(minDistanceInput.value, 10),
      source: source,
    })

    const styleCache = {}
    const clusters = new VectorLayer({
      source: clusterSource,
      style: function (feature) {
        const size = feature.get("features").length
        let style = styleCache[size]
        if (!style) {
          style = new Style({
            image: new CircleStyle({
              radius: 10,
              stroke: new Stroke({
                color: "#fff",
              }),
              fill: new Fill({
                color: "#3399CC",
              }),
            }),
            text: new Text({
              text: size.toString(),
              fill: new Fill({
                color: "#fff",
              }),
            }),
          })
          styleCache[size] = style
        }
        return style
      },
    })

    const raster = new TileLayer({
      source: new OSM(),
    })

    const map = new Map({
      layers: [raster, clusters],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
      }),
    })

    const distanceHandler = function () {
      clusterSource.setDistance(parseInt(distanceInput.value, 10))
    }
    distanceInput.addEventListener("input", distanceHandler)
    distanceInput.addEventListener("change", distanceHandler)

    const minDistanceHandler = function () {
      clusterSource.setMinDistance(parseInt(minDistanceInput.value, 10))
    }
    minDistanceInput.addEventListener("input", minDistanceHandler)
    minDistanceInput.addEventListener("change", minDistanceHandler)

    map.on("click", (e) => {
      clusters.getFeatures(e.pixel).then((clickedFeatures) => {
        if (clickedFeatures.length) {
          const features = clickedFeatures[0].get("features")
          if (features.length > 1) {
            const extent = boundingExtent(
              features.map((r) => r.getGeometry().getCoordinates())
            )
            map
              .getView()
              .fit(extent, { duration: 1000, padding: [50, 50, 50, 50] })
          }
        }
      })
    })
  },
}
</script>
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# 3.getBottomLeft

样式渲染器

查看代码详情
<template>
  <div>
    <div ref="map" class="map"></div>
    <div id="info">&nbsp;</div>
  </div>
</template>

<script>
export default {
  mounted() {
    let {
      format: { GeoJSON },
      Map,
      View,
      layer: { Vector: VectorLayer },
      source: { Vector: VectorSource },
      style: { Fill, Stroke, Style },
      extent: { getBottomLeft, getHeight, getWidth },
      render: { toContext },
    } = ol;

    const fill = new Fill();
    const stroke = new Stroke({
      color: "rgba(255,255,255,0.8)",
      width: 2,
    });
    const style = new Style({
      renderer: function (pixelCoordinates, state) {
        const context = state.context;
        const geometry = state.geometry.clone();
        geometry.setCoordinates(pixelCoordinates);
        const extent = geometry.getExtent();
        const width = getWidth(extent);
        const height = getHeight(extent);
        const flag = state.feature.get("flag");
        if (!flag || height < 1 || width < 1) {
          return;
        }
        context.save();
        const renderContext = toContext(context, {
          pixelRatio: 1,
        });
        renderContext.setFillStrokeStyle(fill, stroke);
        renderContext.drawGeometry(geometry);
        context.clip();
        const bottomLeft = getBottomLeft(extent);
        const left = bottomLeft[0];
        const bottom = bottomLeft[1];
        context.drawImage(flag, left, bottom, width, height);
        context.restore();
      },
    });

    const vectorLayer = new VectorLayer({
      source: new VectorSource({
        url: "https://openlayersbook.github.io/openlayers_book_samples/assets/data/countries.geojson",
        format: new GeoJSON(),
      }),
      style: style,
    });
    vectorLayer.getSource().on("addfeature", function (event) {
      const feature = event.feature;
      const img = new Image();
      img.onload = function () {
        feature.set("flag", img);
      };
      img.src =
        "https://flagcdn.com/w320/" +
        feature.get("iso_a2").toLowerCase() +
        ".png";
    });

    new Map({
      layers: [vectorLayer],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 1,
      }),
    });
  },
};
</script>
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