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In response to a Stack Overflow question regarding centering a map given a GeoJSON object.
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .feature { | |
| fill: #ccc; | |
| } | |
| .mesh { | |
| fill: none; | |
| stroke: #fff; | |
| stroke-width: .5px; | |
| stroke-linejoin: round; | |
| } | |
| .outline { | |
| fill: #ddd; | |
| stroke: #000; | |
| stroke-width: 1.5px; | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="//d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 1200, | |
| height = 630; | |
| var mapWidth = width * 0.5, | |
| mapHeight = height; | |
| var projection = d3.geo.conicEqualArea(); | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("/mbostock/raw/4090846/us.json", function(error, us) { | |
| if (error) throw error; | |
| var states = topojson.feature(us, us.objects.states), | |
| state = states.features.filter(function(d) { return d.id === 25; })[0]; | |
| var b = path.bounds(state), | |
| centroid = d3.geo.centroid(state), | |
| pOffset = b[1][1] - b[0][1] * 0.3; | |
| console.log(b, pOffset); | |
| projection | |
| .parallels([b[1][1] - pOffset, b[0][1] + pOffset]) | |
| .rotate([-1 * centroid[0]]) | |
| .scale(1) | |
| .translate([0, 0]); | |
| b = path.bounds(state) | |
| var s = 0.9 / Math.max((b[1][0] - b[0][0]) / mapWidth, (b[1][1] - b[0][1]) / mapHeight), | |
| t = [(mapWidth - s * (b[1][0] + b[0][0])) / 2, (mapHeight - s * (b[1][1] + b[0][1])) / 2]; | |
| projection | |
| .scale(s) | |
| .translate(t); | |
| svg.append("path") | |
| .datum(states) | |
| .attr("class", "feature") | |
| .attr("d", path); | |
| svg.append("path") | |
| .datum(topojson.mesh(us, us.objects.states, function(a, b) { return a !== b; })) | |
| .attr("class", "mesh") | |
| .attr("d", path); | |
| svg.append("path") | |
| .datum(state) | |
| .attr("class", "outline") | |
| .attr("d", path); | |
| }); | |
| </script> |
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