Openlayers学习笔记

# 十七.Raster

# 1.阴影浮雕

查看代码详情 
<template>
  <div>
    <div ref="map" class="map"></div>
    <table class="controls">
      <tr>
        <td><label for="vert">vertical exaggeration:</label></td>
        <td><input ref="vert" type="range" min="1" max="5" value="1" /></td>
        <td><span ref="vertOut"></span> x</td>
      </tr>
      <tr>
        <td><label for="sunEl">sun elevation:</label></td>
        <td><input ref="sunEl" type="range" min="0" max="90" value="45" /></td>
        <td><span ref="sunElOut"></span> °</td>
      </tr>
      <tr>
        <td><label for="sunAz">sun azimuth:</label></td>
        <td><input ref="sunAz" type="range" min="0" max="360" value="45" /></td>
        <td><span ref="sunAzOut"></span> °</td>
      </tr>
    </table>
  </div>
</template>
  
  <script>
export default {
  mounted() {
    let {
      Map,
      View,
      layer: { Tile: TileLayer, Image: ImageLayer },
      source: { OSM, Raster, XYZ },
    } = ol;
    function shade(inputs, data) {
      const elevationImage = inputs[0];
      const width = elevationImage.width;
      const height = elevationImage.height;
      const elevationData = elevationImage.data;
      const shadeData = new Uint8ClampedArray(elevationData.length);
      const dp = data.resolution * 2;
      const maxX = width - 1;
      const maxY = height - 1;
      const pixel = [0, 0, 0, 0];
      const twoPi = 2 * Math.PI;
      const halfPi = Math.PI / 2;
      const sunEl = (Math.PI * data.sunEl) / 180;
      const sunAz = (Math.PI * data.sunAz) / 180;
      const cosSunEl = Math.cos(sunEl);
      const sinSunEl = Math.sin(sunEl);
      let pixelX,
        pixelY,
        x0,
        x1,
        y0,
        y1,
        offset,
        z0,
        z1,
        dzdx,
        dzdy,
        slope,
        aspect,
        cosIncidence,
        scaled;
      function calculateElevation(pixel) {
        return pixel[0] + pixel[1] * 2 + pixel[2] * 3;
      }
      for (pixelY = 0; pixelY <= maxY; ++pixelY) {
        y0 = pixelY === 0 ? 0 : pixelY - 1;
        y1 = pixelY === maxY ? maxY : pixelY + 1;
        for (pixelX = 0; pixelX <= maxX; ++pixelX) {
          x0 = pixelX === 0 ? 0 : pixelX - 1;
          x1 = pixelX === maxX ? maxX : pixelX + 1;
          offset = (pixelY * width + x0) * 4;
          pixel[0] = elevationData[offset];
          pixel[1] = elevationData[offset + 1];
          pixel[2] = elevationData[offset + 2];
          pixel[3] = elevationData[offset + 3];
          z0 = data.vert * calculateElevation(pixel);
          offset = (pixelY * width + x1) * 4;
          pixel[0] = elevationData[offset];
          pixel[1] = elevationData[offset + 1];
          pixel[2] = elevationData[offset + 2];
          pixel[3] = elevationData[offset + 3];
          z1 = data.vert * calculateElevation(pixel);
          dzdx = (z1 - z0) / dp;
          offset = (y0 * width + pixelX) * 4;
          pixel[0] = elevationData[offset];
          pixel[1] = elevationData[offset + 1];
          pixel[2] = elevationData[offset + 2];
          pixel[3] = elevationData[offset + 3];
          z0 = data.vert * calculateElevation(pixel);
          offset = (y1 * width + pixelX) * 4;
          pixel[0] = elevationData[offset];
          pixel[1] = elevationData[offset + 1];
          pixel[2] = elevationData[offset + 2];
          pixel[3] = elevationData[offset + 3];
          z1 = data.vert * calculateElevation(pixel);
          dzdy = (z1 - z0) / dp;
          slope = Math.atan(Math.sqrt(dzdx * dzdx + dzdy * dzdy));
          aspect = Math.atan2(dzdy, -dzdx);
          if (aspect < 0) {
            aspect = halfPi - aspect;
          } else if (aspect > halfPi) {
            aspect = twoPi - aspect + halfPi;
          } else {
            aspect = halfPi - aspect;
          }
          cosIncidence =
            sinSunEl * Math.cos(slope) +
            cosSunEl * Math.sin(slope) * Math.cos(sunAz - aspect);
          offset = (pixelY * width + pixelX) * 4;
          scaled = 255 * cosIncidence;
          shadeData[offset] = scaled;
          shadeData[offset + 1] = scaled;
          shadeData[offset + 2] = scaled;
          shadeData[offset + 3] = elevationData[offset + 3];
        }
      }
      return { data: shadeData, width: width, height: height };
    }
    const elevation = new XYZ({
      url: "https://{a-d}.tiles.mapbox.com/v3/aj.sf-dem/{z}/{x}/{y}.png",
      crossOrigin: "anonymous",
    });
    const raster = new Raster({
      sources: [elevation],
      operationType: "image",
      operation: shade,
    });
    const map = new Map({
      target: this.$refs.map,
      layers: [
        new TileLayer({
          source: new OSM(),
        }),
        new ImageLayer({
          opacity: 0.3,
          source: raster,
        }),
      ],
      view: new View({
        extent: [-13675026, 4439648, -13580856, 4580292],
        center: [-13615645, 4497969],
        minZoom: 10,
        maxZoom: 16,
        zoom: 13,
      }),
    });
    const controlIds = ["vert", "sunEl", "sunAz"];
    const controls = {};
    controlIds.forEach(
      function (id) {
        const control = this.$refs[id];
        const output = this.$refs[id + "Out"];
        const listener = function () {
          output.innerText = control.value;
          raster.changed();
        };
        control.addEventListener("input", listener);
        control.addEventListener("change", listener);
        output.innerText = control.value;
        controls[id] = control;
      }.bind(this)
    );
    raster.on("beforeoperations", function (event) {
      const data = event.data;
      data.resolution = event.resolution;
      for (const id in controls) {
        data[id] = Number(controls[id].value);
      }
    });
  },
};
</script>
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# 2.光栅源

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

<script>
export default {
  mounted() {
    let {
      Map,
      View,
      layer: { Tile: TileLayer, Image: ImageLayer },
      source: { XYZ, Raster: RasterSource },
    } = ol

    const minVgi = 0
    const maxVgi = 0.5
    const bins = 10
    function vgi(pixel) {
      const r = pixel[0] / 255
      const g = pixel[1] / 255
      const b = pixel[2] / 255
      return (2 * g - r - b) / (2 * g + r + b)
    }
    function summarize(value, counts) {
      const min = counts.min
      const max = counts.max
      const num = counts.values.length
      if (value < min) {
      } else if (value >= max) {
        counts.values[num - 1] += 1
      } else {
        const index = Math.floor((value - min) / counts.delta)
        counts.values[index] += 1
      }
    }
    const attributions =
      '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' +
      '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>'
    const aerial = new XYZ({
      attributions: attributions,
      url:
        "https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key=" +
        mapkeys.maptiler,
      maxZoom: 20,
      crossOrigin: "",
    })
    const raster = new RasterSource({
      sources: [aerial],
      operation: function (pixels, data) {
        const pixel = pixels[0]
        const value = vgi(pixel)
        summarize(value, data.counts)
        if (value >= data.threshold) {
          pixel[0] = 0
          pixel[1] = 255
          pixel[2] = 0
          pixel[3] = 128
        } else {
          pixel[3] = 0
        }
        return pixel
      },
      lib: {
        vgi: vgi,
        summarize: summarize,
      },
    })
    raster.set("threshold", 0.25)
    function createCounts(min, max, num) {
      const values = new Array(num)
      for (let i = 0; i < num; ++i) {
        values[i] = 0
      }
      return {
        min: min,
        max: max,
        values: values,
        delta: (max - min) / num,
      }
    }
    raster.on("beforeoperations", function (event) {
      event.data.counts = createCounts(minVgi, maxVgi, bins)
      event.data.threshold = raster.get("threshold")
    })
    raster.on("afteroperations", function (event) {
      schedulePlot(event.resolution, event.data.counts, event.data.threshold)
    })
    const map = new Map({
      layers: [
        new TileLayer({
          source: aerial,
        }),
        new ImageLayer({
          source: raster,
        }),
      ],
      target: this.$refs.map,
      view: new View({
        center: [-9651695, 4937351],
        zoom: 13,
        minZoom: 12,
        maxZoom: 19,
      }),
    })
    let timer = null
    function schedulePlot(resolution, counts, threshold) {
      if (timer) {
        clearTimeout(timer)
        timer = null
      }
      timer = setTimeout(
        plot.bind(null, resolution, counts, threshold),
        1000 / 60
      )
    }
    const barWidth = 15
    const plotHeight = 150
    const chart = d3
      .select("#plot")
      .append("svg")
      .attr("width", barWidth * bins)
      .attr("height", plotHeight)
    const chartRect = chart.node().getBoundingClientRect()
    const tip = d3.select(document.body).append("div").attr("class", "tip")
    function plot(resolution, counts, threshold) {
      const yScale = d3
        .scaleLinear()
        .domain([0, d3.max(counts.values)])
        .range([0, plotHeight])
      const bar = chart.selectAll("rect").data(counts.values)
      bar.enter().append("rect")
      bar
        .attr("class", function (count, index) {
          const value = counts.min + index * counts.delta
          return "bar" + (value >= threshold ? " selected" : "")
        })
        .attr("width", barWidth - 2)
      bar
        .transition()
        .attr("transform", function (value, index) {
          return (
            "translate(" +
            index * barWidth +
            ", " +
            (plotHeight - yScale(value)) +
            ")"
          )
        })
        .attr("height", yScale)
      bar.on("mousemove", function () {
        const index = bar.nodes().indexOf(this)
        const threshold = counts.min + index * counts.delta
        if (raster.get("threshold") !== threshold) {
          raster.set("threshold", threshold)
          raster.changed()
        }
      })
      bar.on("mouseover", function (event) {
        const index = bar.nodes().indexOf(this)
        let area = 0
        for (let i = counts.values.length - 1; i >= index; --i) {
          area += resolution * resolution * counts.values[i]
        }
        tip.html(message(counts.min + index * counts.delta, area))
        tip.style("display", "block")
        tip
          .transition()
          .style(
            "left",
            chartRect.left + index * barWidth + barWidth / 2 + "px"
          )
          .style("top", event.y - 60 + "px")
          .style("opacity", 1)
      })
      bar.on("mouseout", function () {
        tip
          .transition()
          .style("opacity", 0)
          .on("end", function () {
            tip.style("display", "none")
          })
      })
    }
    function message(value, area) {
      const acres = (area / 4046.86)
        .toFixed(0)
        .replace(/\B(?=(\d{3})+(?!\d))/g, ",")
      return acres + " acres at<br>" + value.toFixed(2) + " VGI or above"
    }
  },
}
</script>
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# 3.颜色处理

查看代码详情 
<template>
  <div>
    <div ref="map" class="map"></div>
    <table class="controls">
      <tr>
        <td><label for="hue">颜色</label></td>
        <td><input id="hue" type="range" min="-180" max="180" value="0" /></td>
        <td><span id="hueOut"></span> °&nbsp;</td>
      </tr>
      <tr>
        <td><label for="chroma">色度</label></td>
        <td>
          <input id="chroma" type="range" min="0" max="100" value="100" />
        </td>
        <td><span id="chromaOut"></span> %</td>
      </tr>
      <tr>
        <td><label for="lightness">亮度</label></td>
        <td>
          <input id="lightness" type="range" min="0" max="100" value="100" />
        </td>
        <td><span id="lightnessOut"></span> %</td>
      </tr>
    </table>
  </div>
</template>

<script>
export default {
  mounted() {
    let {
      Map,
      View,
      layer: { Image: ImageLayer },
      source: { Raster: RasterSource, Stamen },
    } = ol
    const Xn = 0.95047
    const Yn = 1
    const Zn = 1.08883
    const t0 = 4 / 29
    const t1 = 6 / 29
    const t2 = 3 * t1 * t1
    const t3 = t1 * t1 * t1
    const twoPi = 2 * Math.PI

    function rgb2hcl(pixel) {
      const red = rgb2xyz(pixel[0])
      const green = rgb2xyz(pixel[1])
      const blue = rgb2xyz(pixel[2])
      const x = xyz2lab(
        (0.4124564 * red + 0.3575761 * green + 0.1804375 * blue) / Xn
      )
      const y = xyz2lab(
        (0.2126729 * red + 0.7151522 * green + 0.072175 * blue) / Yn
      )
      const z = xyz2lab(
        (0.0193339 * red + 0.119192 * green + 0.9503041 * blue) / Zn
      )
      const l = 116 * y - 16
      const a = 500 * (x - y)
      const b = 200 * (y - z)
      const c = Math.sqrt(a * a + b * b)
      let h = Math.atan2(b, a)
      if (h < 0) {
        h += twoPi
      }
      pixel[0] = h
      pixel[1] = c
      pixel[2] = l
      return pixel
    }

    function hcl2rgb(pixel) {
      const h = pixel[0]
      const c = pixel[1]
      const l = pixel[2]
      const a = Math.cos(h) * c
      const b = Math.sin(h) * c
      let y = (l + 16) / 116
      let x = isNaN(a) ? y : y + a / 500
      let z = isNaN(b) ? y : y - b / 200
      y = Yn * lab2xyz(y)
      x = Xn * lab2xyz(x)
      z = Zn * lab2xyz(z)
      pixel[0] = xyz2rgb(3.2404542 * x - 1.5371385 * y - 0.4985314 * z)
      pixel[1] = xyz2rgb(-0.969266 * x + 1.8760108 * y + 0.041556 * z)
      pixel[2] = xyz2rgb(0.0556434 * x - 0.2040259 * y + 1.0572252 * z)
      return pixel
    }

    function xyz2lab(t) {
      return t > t3 ? Math.pow(t, 1 / 3) : t / t2 + t0
    }

    function lab2xyz(t) {
      return t > t1 ? t * t * t : t2 * (t - t0)
    }

    function rgb2xyz(x) {
      return (x /= 255) <= 0.04045
        ? x / 12.92
        : Math.pow((x + 0.055) / 1.055, 2.4)
    }

    function xyz2rgb(x) {
      return (
        255 *
        (x <= 0.0031308 ? 12.92 * x : 1.055 * Math.pow(x, 1 / 2.4) - 0.055)
      )
    }

    const raster = new RasterSource({
      sources: [
        new Stamen({
          layer: "watercolor",
        }),
      ],
      operation: function (pixels, data) {
        const hcl = rgb2hcl(pixels[0])

        let h = hcl[0] + (Math.PI * data.hue) / 180
        if (h < 0) {
          h += twoPi
        } else if (h > twoPi) {
          h -= twoPi
        }
        hcl[0] = h

        hcl[1] *= data.chroma / 100
        hcl[2] *= data.lightness / 100

        return hcl2rgb(hcl)
      },
      lib: {
        rgb2hcl: rgb2hcl,
        hcl2rgb: hcl2rgb,
        rgb2xyz: rgb2xyz,
        lab2xyz: lab2xyz,
        xyz2lab: xyz2lab,
        xyz2rgb: xyz2rgb,
        Xn: Xn,
        Yn: Yn,
        Zn: Zn,
        t0: t0,
        t1: t1,
        t2: t2,
        t3: t3,
        twoPi: twoPi,
      },
    })

    const controls = {}

    raster.on("beforeoperations", function (event) {
      const data = event.data
      for (const id in controls) {
        data[id] = Number(controls[id].value)
      }
    })

    const map = new Map({
      layers: [
        new ImageLayer({
          source: raster,
        }),
      ],
      target: this.$refs.map,
      view: new View({
        center: [0, 2500000],
        zoom: 2,
        maxZoom: 18,
      }),
    })

    const controlIds = ["hue", "chroma", "lightness"]
    controlIds.forEach(function (id) {
      const control = document.getElementById(id)
      const output = document.getElementById(id + "Out")
      const listener = function () {
        output.innerText = control.value
        raster.changed()
      }
      control.addEventListener("input", listener)
      control.addEventListener("change", listener)
      output.innerText = control.value
      controls[id] = control
    })
  },
}
</script>
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← 十八.TileJSON →