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# Custom Projection

This demo illustrates how to implement a custom projection. To do it, set the aspectRatio, to, and from properties. TheÂ Wagner-VI projection is used in this example.

www.wikipedia.org
Backend API
<template> <DxVectorMap id="vector-map" :projection="customProjection" title="Wagner VI projection" > <DxLayer :data-source="world" /> <DxLayer :data-source="coordLinesData" :hover-enabled="false" :border-width="1" color="#aaa" /> <DxExport :enabled="true"/> </DxVectorMap> </template> <script setup lang="ts"> import { DxVectorMap, DxLayer, DxExport, } from 'devextreme-vue/vector-map'; import * as mapsData from 'devextreme-dist/js/vectormap-data/world.js'; import { coordLinesData } from './data.ts'; const world = mapsData.world; const RADIANS = Math.PI / 180; const WAGNER_6_P_LAT = Math.PI / Math.sqrt(3); const WAGNER_6_U_LAT = 2 / Math.sqrt(3) - 0.1; const customProjection = { aspectRatio: 2, to(coordinates) { const x = coordinates[0] * RADIANS; const y = Math.min(Math.max(coordinates[1] * RADIANS, -WAGNER_6_P_LAT), +WAGNER_6_P_LAT); const t = y / Math.PI; return [ (x / Math.PI) * Math.sqrt(1 - 3 * t * t), (y * 2) / Math.PI, ]; }, from(coordinates) { const x = coordinates[0]; const y = Math.min(Math.max(coordinates[1], -WAGNER_6_U_LAT), +WAGNER_6_U_LAT); const t = y / 2; return [ (x * Math.PI) / Math.sqrt(1 - 3 * t * t) / RADIANS, (y * Math.PI) / 2 / RADIANS, ]; }, }; </script> <style> #vector-map { height: 400px; } </style>
window.exports = window.exports || {}; window.config = { transpiler: 'plugin-babel', meta: { '*.vue': { loader: 'vue-loader', }, '*.ts': { loader: 'demo-ts-loader', }, '*.svg': { loader: 'svg-loader', }, 'devextreme/time_zone_utils.js': { 'esModule': true, }, 'devextreme/localization.js': { 'esModule': true, }, 'devextreme/viz/palette.js': { 'esModule': true, }, 'devextreme-dist/js/vectormap-data/*': { 'esModule': true, }, }, paths: { 'root:': '../../../../', 'npm:': 'https://unpkg.com/', }, map: { 'vue': 'npm:vue@3.2.47/dist/vue.esm-browser.js', 'vue-loader': 'npm:dx-systemjs-vue-browser@1.1.1/index.js', 'demo-ts-loader': 'root:utils/demo-ts-loader.js', 'svg-loader': 'root:utils/svg-loader.js', 'devextreme-dist/js/vectormap-data': 'npm:devextreme-dist@24.1.4/js/vectormap-data', 'mitt': 'npm:mitt/dist/mitt.umd.js', 'rrule': 'npm:rrule@2.6.4/dist/es5/rrule.js', 'luxon': 'npm:luxon@1.28.1/build/global/luxon.min.js', 'es6-object-assign': 'npm:es6-object-assign@1.1.0', 'devextreme': 'npm:devextreme@24.1.4/cjs', 'devextreme-vue': 'npm:devextreme-vue@24.1.4/cjs', 'jszip': 'npm:jszip@3.10.1/dist/jszip.min.js', 'devextreme-quill': 'npm:devextreme-quill@1.7.1/dist/dx-quill.min.js', 'devexpress-diagram': 'npm:devexpress-diagram@2.2.10/dist/dx-diagram.js', 'devexpress-gantt': 'npm:devexpress-gantt@4.1.56/dist/dx-gantt.js', '@devextreme/runtime': 'npm:@devextreme/runtime@3.0.13', 'inferno': 'npm:inferno@7.4.11/dist/inferno.min.js', 'inferno-compat': 'npm:inferno-compat/dist/inferno-compat.min.js', 'inferno-create-element': 'npm:inferno-create-element@7.4.11/dist/inferno-create-element.min.js', 'inferno-dom': 'npm:inferno-dom/dist/inferno-dom.min.js', 'inferno-hydrate': 'npm:inferno-hydrate@7.4.11/dist/inferno-hydrate.min.js', 'inferno-clone-vnode': 'npm:inferno-clone-vnode/dist/inferno-clone-vnode.min.js', 'inferno-create-class': 'npm:inferno-create-class/dist/inferno-create-class.min.js', 'inferno-extras': 'npm:inferno-extras/dist/inferno-extras.min.js', 'plugin-babel': 'npm:systemjs-plugin-babel@0.0.25/plugin-babel.js', 'systemjs-babel-build': 'npm:systemjs-plugin-babel@0.0.25/systemjs-babel-browser.js', // Prettier 'prettier/standalone': 'npm:prettier@2.8.8/standalone.js', 'prettier/parser-html': 'npm:prettier@2.8.8/parser-html.js', }, packages: { 'devextreme-vue': { main: 'index.js', }, 'devextreme': { defaultExtension: 'js', }, 'devextreme/events/utils': { main: 'index', }, 'devextreme/events': { main: 'index', }, 'es6-object-assign': { main: './index.js', defaultExtension: 'js', }, }, packageConfigPaths: [ 'npm:@devextreme/*/package.json', 'npm:@devextreme/runtime@3.0.13/inferno/package.json', ], babelOptions: { sourceMaps: false, stage0: true, }, }; System.config(window.config);
export const coordLinesData = { type: 'FeatureCollection', features: [], }; // add meridians for (let longitude = -180; longitude <= 180; longitude += 30) { const lineCoords = []; for (let latitude = -90; latitude <= 90; latitude += 5) { lineCoords.push([longitude, latitude]); } coordLinesData.features.push({ geometry: { type: 'LineString', coordinates: lineCoords, }, }); } // add parallels for (let latitude = -90; latitude <= 90; latitude += 30) { coordLinesData.features.push({ geometry: { type: 'LineString', coordinates: [[-180, latitude], [180, latitude]], }, }); }
import { createApp } from 'vue'; import App from './App.vue'; createApp(App).mount('#app');
<!DOCTYPE html> <html lang="en"> <head> <title>DevExtreme Demo</title> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=5.0" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/24.1.4/css/dx.light.css" /> <script src="https://unpkg.com/typescript@4.9.5/lib/typescript.js"></script> <script type="module"> import * as vueCompilerSFC from "https://unpkg.com/@vue/compiler-sfc@3.4.16/dist/compiler-sfc.esm-browser.js"; window.vueCompilerSFC = vueCompilerSFC; </script> <script src="https://unpkg.com/core-js@2.6.12/client/shim.min.js"></script> <script src="https://unpkg.com/systemjs@0.21.3/dist/system.js"></script> <script type="text/javascript" src="config.js"></script> <script type="text/javascript"> System.import("./index.ts"); </script> </head> <body class="dx-viewport"> <div class="demo-container"> <div id="app"></div> </div> </body> </html>