feat(source): hexagon

package.json

@@ -101,6 +101,7 @@
     "@turf/invariant": "^6.1.2",
     "@turf/meta": "^6.0.2",
     "d3-dsv": "^1.0.10",
+    "d3-hexbin": "^0.2.2",
     "earcut": "^2.1.3",
     "fecha": "^2.3.3",
     "gl-matrix": "^2.4.1",

src/geo/project.js

@@ -13,5 +13,20 @@ export function aProjectFlat(lnglat) {
   d = 0.5;
   x = scale * (a * x + b) - 215440491;
   y = scale * (c * y + d) - 106744817;
-  return { x, y };
+  return { x: parseInt(x), y: parseInt(y) };
+}
+export function unProjectFlat(px) {
+  const a = 0.5 / Math.PI,
+    b = 0.5,
+    c = -0.5 / Math.PI;
+  let d = 0.5;
+  const scale = 256 << 20;
+  let [ x, y ] = px;
+  x = ((x + 215440491) / scale - b) / a;
+  y = ((y + 106744817) / scale - d) / c;
+  y = (Math.atan(Math.pow(Math.E, y)) - (Math.PI / 4)) * 2;
+  d = Math.PI / 180;
+  const lat = y / d;
+  const lng = x / d;
+  return [ lng, lat ];
 }

src/source/index.js

@@ -7,7 +7,7 @@ import json from './parser/json';
 import raster from './parser/raster';
 
 import { registerTransform, registerParser } from './factory';
-import { aggregatorToGrid } from './transform/grid-aggregator';
+import { aggregatorToGrid } from './transform/grid';
 import { map } from './transform/map';
 
 registerParser('geojson', geojson);

src/source/transform/hexagon.js

@@ -0,0 +1,41 @@
+import { hexbin } from 'd3-hexbin';
+import { aProjectFlat, unProjectFlat } from '../../geo/project';
+import * as statistics from './statistics';
+const R_EARTH = 6378000;
+export function pointToHexbin(data, option) {
+  const dataArray = data.dataArray;
+  const { size = 10 } = option;
+  const pixlSize = size / (2 * Math.PI * R_EARTH) * (256 << 20) / 2;
+  const screenPoints = dataArray.map(point => {
+    const { x, y } = aProjectFlat(point.coordinates);
+    return {
+      ...point,
+      coordinates: [ x, y ]
+    };
+  });
+
+  const newHexbin = hexbin()
+    .radius(pixlSize)
+    .x(d => d.coordinates[0])
+    .y(d => d.coordinates[1]);
+  const hexbinBins = newHexbin(screenPoints);
+  const result = {
+    size: pixlSize
+  };
+  result.dataArray = hexbinBins.map((hex, index) => {
+    if (option.field && option.method) {
+      const columns = getColumn(hex, option.field);
+      hex[option.method] = statistics[option.method](columns);
+    }
+    return {
+      coordinates: unProjectFlat([ hex.x, hex.y ]),
+      id: index + 1
+    };
+  });
+  return result;
+}
+function getColumn(data, columnName) {
+  return data.map(item => {
+    return item[columnName];
+  });
+}

test/unit/source/transfrom/hexagon.js

@@ -0,0 +1,21 @@
+import { expect } from 'chai';
+import { pointData } from '../../../asset/data/point';
+import { pointToHexbin } from '../../../../src/source/transform/hexagon';
+describe('hexagon  Test', function() {
+
+  it('pointToHexbin', function() {
+    const dataArray = pointData.map(item => {
+      const lng = 1e-6 * (250 * item.grid_x + 125),
+        lat = 1e-6 * (250 * item.grid_y + 125);
+      return {
+        v: item.count * 1,
+        coordinates: [ lng, lat ]
+      };
+    });
+
+    const data = {
+      dataArray
+    };
+    const hexgonGrid = pointToHexbin(data, { size: 100, field: 'count', method: 'sum' });
+  });
+});