Openlayers学习笔记

# 三.地震标记

# 1.地震图

解析 KML 文件并将要素呈现为矢量图层。给定图层 a style 以相对于震级的大小来渲染地震位置。

查看代码详情 
<template>
  <div ref="map" class="map"><div id="info"></div></div>
</template>
  
  <script>
let {
  Map,
  View,
  layer: { Tile: TileLayer, Vector: VectorLayer },
  source: { Stamen, Vector: VectorSource },
  style: { Circle: CircleStyle, Fill, Stroke, Style },
  format: { KML },
} = ol;
export default {
  mounted() {
    const styleCache = {};
    const styleFunction = function (feature) {
      const name = feature.get("name");
      const magnitude = parseFloat(name.substr(2));
      const radius = 5 + 20 * (magnitude - 5);
      let style = styleCache[radius];
      if (!style) {
        style = new Style({
          image: new CircleStyle({
            radius: radius,
            fill: new Fill({
              color: "rgba(255, 153, 0, 0.4)",
            }),
            stroke: new Stroke({
              color: "rgba(255, 204, 0, 0.2)",
              width: 1,
            }),
          }),
        });
        styleCache[radius] = style;
      }
      return style;
    };

    const map = new Map({
      layers: [
        new TileLayer({
          source: new Stamen({
            layer: "toner",
          }),
        }),
        new VectorLayer({
          source: new VectorSource({
            url: this.$withBase("/data/kml/2012_Earthquakes_Mag5.kml"),
            format: new KML({
              extractStyles: false,
            }),
          }),
          style: styleFunction,
        }),
      ],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
      }),
    });

    // const info = $("#info");
    // info.tooltip({
    //   animation: false,
    //   trigger: "manual",
    // });

    // const displayFeatureInfo = function (pixel) {
    //   info.css({
    //     left: pixel[0] + "px",
    //     top: pixel[1] - 15 + "px",
    //   });
    //   const feature = map.forEachFeatureAtPixel(pixel, function (feature) {
    //     return feature;
    //   });
    //   if (feature) {
    //     info.attr("data-original-title", feature.get("name")).tooltip("show");
    //   } else {
    //     info.tooltip("hide");
    //   }
    // };

    // map.on("pointermove", function (evt) {
    //   if (evt.dragging) {
    //     info.tooltip("hide");
    //     return;
    //   }
    //   displayFeatureInfo(map.getEventPixel(evt.originalEvent));
    // });

    // map.on("click", function (evt) {
    //   displayFeatureInfo(evt.pixel);
    // });
  },
};
</script>
  <style></style>
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# 2.自定义地震图

使用 toContext 创建自定义图标符号

查看代码详情 
<template>
  <div ref="map" class="map"></div>
</template>
  
  <script>
let {
  format: { KML },
  geom: { Polygon },
  Map,
  View,
  layer: { Tile: TileLayer, Vector: VectorLayer },
  source: { Stamen, Vector: VectorSource },
  style: { Fill, Icon, Stroke, Style },
  render: { toContext },
} = ol;
export default {
  mounted() {
    const symbol = [
      [0, 0],
      [4, 2],
      [6, 0],
      [10, 5],
      [6, 3],
      [4, 5],
      [0, 0],
    ];
    let scale;
    const scaleFunction = function (coordinate) {
      return [coordinate[0] * scale, coordinate[1] * scale];
    };
    const styleCache = {};
    const map = new Map({
      layers: [
        new TileLayer({
          source: new Stamen({
            layer: "toner",
          }),
        }),
        new VectorLayer({
          source: new VectorSource({
            url: this.$withBase("/data/kml/2012_Earthquakes_Mag5.kml"),
            format: new KML({
              extractStyles: false,
            }),
          }),
          style: function (feature) {
            const name = feature.get("name");
            const magnitude = parseFloat(name.substr(2));
            const size = parseInt(10 + 40 * (magnitude - 5), 10);
            scale = size / 10;
            let style = styleCache[size];
            if (!style) {
              const canvas = document.createElement("canvas");
              const vectorContext = toContext(canvas.getContext("2d"), {
                size: [size, size],
                pixelRatio: 1,
              });
              vectorContext.setStyle(
                new Style({
                  fill: new Fill({ color: "rgba(255, 153, 0, 0.4)" }),
                  stroke: new Stroke({
                    color: "rgba(255, 204, 0, 0.2)",
                    width: 2,
                  }),
                })
              );
              vectorContext.drawGeometry(
                new Polygon([symbol.map(scaleFunction)])
              );
              style = new Style({
                image: new Icon({
                  img: canvas,
                  imgSize: [size, size],
                  rotation: 1.2,
                }),
              });
              styleCache[size] = style;
            }
            return style;
          },
        }),
      ],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
      }),
    });
  },
};
</script>
  <style></style>
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# 3.地震群

查看代码详情 
<template>
  <div ref="map" class="map"></div>
</template>
  
  <script>
let {
  interaction: { Select, defaults: defaultInteractions },
  Map,
  View,
  layer: { Tile: TileLayer, Vector: VectorLayer },
  source: { Cluster, Stamen, Vector: VectorSource },
  style: { Circle: CircleStyle, Fill, RegularShape, Stroke, Style, Text },
  format: { KML },
  extent: { createEmpty, extend, getHeight, getWidth },
} = ol;
export default {
  mounted() {
    const earthquakeFill = new Fill({
      color: "rgba(255, 153, 0, 0.8)",
    });
    const earthquakeStroke = new Stroke({
      color: "rgba(255, 204, 0, 0.2)",
      width: 1,
    });
    const textFill = new Fill({
      color: "#fff",
    });
    const textStroke = new Stroke({
      color: "rgba(0, 0, 0, 0.6)",
      width: 3,
    });
    const invisibleFill = new Fill({
      color: "rgba(255, 255, 255, 0.01)",
    });

    function createEarthquakeStyle(feature) {
      const name = feature.get("name");
      const magnitude = parseFloat(name.substr(2));
      const radius = 5 + 20 * (magnitude - 5);

      return new Style({
        geometry: feature.getGeometry(),
        image: new RegularShape({
          radius1: radius,
          radius2: 3,
          points: 5,
          angle: Math.PI,
          fill: earthquakeFill,
          stroke: earthquakeStroke,
        }),
      });
    }

    let maxFeatureCount;
    let vector = null;
    const calculateClusterInfo = function (resolution) {
      maxFeatureCount = 0;
      const features = vector.getSource().getFeatures();
      let feature, radius;
      for (let i = features.length - 1; i >= 0; --i) {
        feature = features[i];
        const originalFeatures = feature.get("features");
        const extent = createEmpty();
        let j, jj;
        for (j = 0, jj = originalFeatures.length; j < jj; ++j) {
          extend(extent, originalFeatures[j].getGeometry().getExtent());
        }
        maxFeatureCount = Math.max(maxFeatureCount, jj);
        radius = (0.25 * (getWidth(extent) + getHeight(extent))) / resolution;
        feature.set("radius", radius);
      }
    };

    let currentResolution;
    function styleFunction(feature, resolution) {
      if (resolution != currentResolution) {
        calculateClusterInfo(resolution);
        currentResolution = resolution;
      }
      let style;
      const size = feature.get("features").length;
      if (size > 1) {
        style = new Style({
          image: new CircleStyle({
            radius: feature.get("radius"),
            fill: new Fill({
              color: [255, 153, 0, Math.min(0.8, 0.4 + size / maxFeatureCount)],
            }),
          }),
          text: new Text({
            text: size.toString(),
            fill: textFill,
            stroke: textStroke,
          }),
        });
      } else {
        const originalFeature = feature.get("features")[0];
        style = createEarthquakeStyle(originalFeature);
      }
      return style;
    }

    function selectStyleFunction(feature) {
      const styles = [
        new Style({
          image: new CircleStyle({
            radius: feature.get("radius"),
            fill: invisibleFill,
          }),
        }),
      ];
      const originalFeatures = feature.get("features");
      let originalFeature;
      for (let i = originalFeatures.length - 1; i >= 0; --i) {
        originalFeature = originalFeatures[i];
        styles.push(createEarthquakeStyle(originalFeature));
      }
      return styles;
    }

    vector = new VectorLayer({
      source: new Cluster({
        distance: 40,
        source: new VectorSource({
          url: this.$withBase("/data/kml/2012_Earthquakes_Mag5.kml"),
          format: new KML({
            extractStyles: false,
          }),
        }),
      }),
      style: styleFunction,
    });

    const raster = new TileLayer({
      source: new Stamen({
        layer: "toner",
      }),
    });

    const map = new Map({
      layers: [raster, vector],
      interactions: defaultInteractions().extend([
        new Select({
          condition: function (evt) {
            return evt.type == "pointermove" || evt.type == "singleclick";
          },
          style: selectStyleFunction,
        }),
      ]),
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
      }),
    });
  },
};
</script>
  <style></style>
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# 4.地震热图

查看代码详情 
<template>
  <div ref="map" class="map"></div>
</template>
  
  <script>
let {
  Map,
  View,
  layer: { Tile: TileLayer, Heatmap: HeatmapLayer },
  source: { Stamen, Vector: VectorSource },
  format: { KML },
} = ol;
export default {
  mounted() {
    const blur = document.getElementById("blur");
    const radius = document.getElementById("radius");

    const vector = new HeatmapLayer({
      source: new VectorSource({
        url: this.$withBase("/data/kml/2012_Earthquakes_Mag5.kml"),
        format: new KML({
          extractStyles: false,
        }),
      }),
      blur: parseInt(blur.value, 10),
      radius: parseInt(radius.value, 10),
      weight: function (feature) {
        const name = feature.get("name");
        const magnitude = parseFloat(name.substr(2));
        return magnitude - 5;
      },
    });

    new Map({
      layers: [
        new TileLayer({
          source: new Stamen({
            layer: "toner",
          }),
        }),
        vector,
      ],
      target: this.$refs.map,
      view: new View({
        center: [12579156, 3274244],
        zoom: 2,
      }),
    });

    const blurHandler = function () {
      vector.setBlur(parseInt(blur.value, 10));
    };
    blur.addEventListener("input", blurHandler);
    blur.addEventListener("change", blurHandler);

    const radiusHandler = function () {
      vector.setRadius(parseInt(radius.value, 10));
    };
    radius.addEventListener("input", radiusHandler);
    radius.addEventListener("change", radiusHandler);
  },
};
</script>
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