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March 9, 2018 15:05
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" /> | |
| <meta http-equiv="X-UA-Compatible" content="ie=edge"> | |
| <title>Mercator projection example</title> | |
| <style> | |
| body { | |
| margin: 0; | |
| padding: 0; | |
| overflow: hidden; | |
| touch-action: none; | |
| } | |
| canvas { | |
| border: 1px solid black; | |
| display: block; | |
| margin: auto; | |
| } | |
| ; | |
| </style> | |
| </head> | |
| <body> | |
| <script> | |
| // Used to generate colors | |
| let i = 0; | |
| // Adjust the map size to the window size | |
| const MAP_SIZE = Math.min(window.parent.window.innerHeight, window.parent.window.innerWidth); | |
| // Set the projection Radius, force the diameter to be equal to map size. | |
| const R = MAP_SIZE / (2 * Math.PI); | |
| // Diameter of the globe | |
| const D = R * 2 * Math.PI; | |
| // Create a canvas element | |
| const canvas = document.createElement('canvas'); | |
| // Set canvas size | |
| canvas.width = MAP_SIZE; | |
| canvas.height = MAP_SIZE; | |
| // Add the canvas to the DOM | |
| document.body.appendChild(canvas); | |
| // Save a drawing context into the map variable | |
| const map = canvas.getContext('2d'); | |
| Z = 1; | |
| let delta = { | |
| x: 0, | |
| y: 0 | |
| } | |
| let center = [-8, 43]; | |
| let c = _project(center); | |
| // fetch('https://raw.githubusercontent.com/codeforamerica/click_that_hood/master/public/data/spain-provinces.geojson') | |
| // fetch('https://raw.githubusercontent.com/openlayers/openlayers/master/examples/data/geojson/roads-seoul.geojson') | |
| fetch('world.json') | |
| .then(response => response.json()) | |
| .then(data => { | |
| window.data = data; | |
| drawGeoJson(data); | |
| getUserInput(canvas, (dx, dy, dz) => { | |
| if (dz > 0) { | |
| if (Z !== 20) { | |
| Z++; | |
| } | |
| } | |
| if (dz < 0) { | |
| if (Z !== 1) { | |
| Z--; | |
| } | |
| } | |
| if (dz === 0) { | |
| delta.x = fit(delta.x - dx); | |
| delta.y = fit(delta.y - dy); | |
| } | |
| console.log(c); | |
| drawGeoJson(data); | |
| }) | |
| }); | |
| function fit(delta) { | |
| return Math.max(Math.min(delta, D * Z), -D * Z); | |
| } | |
| /** | |
| * Draw a geoJson object, it only supports polygons and MultiPolygons | |
| */ | |
| function drawGeoJson(geoJsonData) { | |
| // let c = _project(center); | |
| map.setTransform(1, 0, 0, 1, 0, 0); | |
| map.scale(Math.pow(2, Z), Math.pow(2, Z)); | |
| map.fillStyle = 'aliceblue'; | |
| map.fillRect(0, 0, canvas.width, canvas.height); | |
| geoJsonData.features.forEach(feature => { | |
| if (feature.geometry.type === 'Polygon') { | |
| drawPolygon(map, feature.geometry.coordinates[0]); | |
| } | |
| if (feature.geometry.type === 'MultiPolygon') { | |
| feature.geometry.coordinates.forEach(coords => drawPolygon(map, coords[0])); | |
| } | |
| if (feature.geometry.type === 'LineString') { | |
| drawLine(map, feature.geometry.coordinates); | |
| } | |
| }); | |
| } | |
| /** | |
| * Given a list of coordinates, draw into a rendering context a polygon. | |
| */ | |
| function drawPolygon(ctx, coords) { | |
| const coordinates = coords.map(x => x); | |
| const initialPoint = project(coordinates.shift()); | |
| ctx.fillStyle = getColor(); | |
| ctx.beginPath(); | |
| ctx.moveTo(initialPoint.x, initialPoint.y); | |
| coordinates.map(project).forEach(point => ctx.lineTo(point.x, point.y)); | |
| ctx.closePath(); | |
| ctx.fill(); | |
| } | |
| /** | |
| * Given a list of coordinates, draw into a rendering context a polygon. | |
| */ | |
| function drawLine(ctx, coords) { | |
| const coordinates = coords.map(x => x); | |
| ctx.strokeStyle = 'black'; | |
| ctx.beginPath(); | |
| const initialPoint = project(coordinates.shift()); | |
| ctx.moveTo(initialPoint.x, initialPoint.y); | |
| coordinates.map(project).forEach(point => ctx.lineTo(point.x, point.y)); | |
| ctx.stroke(); | |
| } | |
| // PROYECCION EN PIXELES | |
| function project(point) { | |
| const p = _project(point); | |
| cx = c.x - (c.x / Math.pow(2, Z)); | |
| cy = c.y - (c.y / Math.pow(2, Z)); | |
| return { | |
| x: (p.x - cx) - delta.x / Math.pow(2, Z), | |
| y: (p.y - cy) - delta.y / Math.pow(2, Z) | |
| } | |
| } | |
| /** | |
| * Webmercator projection. | |
| * Since D === MAP_SIZE this function already returns pixel coordinates in the canvas. | |
| */ | |
| function _project([lon, lat]) { | |
| const sinlat = Math.sin(lat * Math.PI / 180.0); | |
| const x = D * lon / 360.0; | |
| const y = R / 2 * Math.log((1 + sinlat) / (1 - sinlat)); | |
| return { x: (D / 2 + x), y: (D - (D / 2 + y)) } | |
| } | |
| /** | |
| * Generate a color | |
| */ | |
| function getColor() { | |
| return 'mediumseagreen'; //`rgb(${i++ % 255}, ${180}, ${255})`; | |
| } | |
| function getUserInput(canvas, callback) { | |
| var dragging = false; | |
| var xo, yo; | |
| canvas.addEventListener('mousedown', e => { | |
| dragging = true | |
| xo = e.clientX | |
| yo = e.clientY | |
| }, { passive: false }); | |
| canvas.addEventListener('mouseup', () => { | |
| dragging = false; | |
| }, { passive: false }); | |
| canvas.addEventListener('mousemove', e => { | |
| if (dragging) { | |
| let [dx, dy] = [e.clientX - xo, e.clientY - yo] | |
| callback(dx, dy, 0) | |
| xo = e.clientX | |
| yo = e.clientY | |
| } | |
| return false; | |
| }, { passive: false }); | |
| canvas.addEventListener('wheel', e => { | |
| dragging = false; | |
| e.preventDefault(); | |
| if (Math.abs(e.deltaY) < 2) { | |
| return; | |
| } | |
| callback(0, 0, e.deltaY > 0 ? 1 : -1) | |
| }, { passive: false }); | |
| canvas.addEventListener('dblclick', () => { | |
| dragging = false; | |
| callback(0, 0, 1) | |
| }, { passive: false }); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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