Demonstrates the d3.geo.tile plug-in used in conjunction with the d3.geo.mercator projection to clip MapBox Natural Earth II raster tiles. The outline of the United States is loaded in TopoJSON format.
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Clipped Map Tiles
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| d3.geo.tile = function() { | |
| var size = [960, 500], | |
| scale = 256, | |
| translate = [size[0] / 2, size[1] / 2], | |
| zoomDelta = 0; | |
| function tile() { | |
| var z = Math.max(Math.log(scale) / Math.LN2 - 8, 0), | |
| z0 = Math.round(z + zoomDelta), | |
| k = Math.pow(2, z - z0 + 8), | |
| origin = [(translate[0] - scale / 2) / k, (translate[1] - scale / 2) / k], | |
| tiles = [], | |
| cols = d3.range(Math.max(0, Math.floor(-origin[0])), Math.max(0, Math.ceil(size[0] / k - origin[0]))), | |
| rows = d3.range(Math.max(0, Math.floor(-origin[1])), Math.max(0, Math.ceil(size[1] / k - origin[1]))); | |
| rows.forEach(function(y) { | |
| cols.forEach(function(x) { | |
| tiles.push([x, y, z0]); | |
| }); | |
| }); | |
| tiles.translate = origin; | |
| tiles.scale = k; | |
| return tiles; | |
| } | |
| tile.size = function(_) { | |
| if (!arguments.length) return size; | |
| size = _; | |
| return tile; | |
| }; | |
| tile.scale = function(_) { | |
| if (!arguments.length) return scale; | |
| scale = _; | |
| return tile; | |
| }; | |
| tile.translate = function(_) { | |
| if (!arguments.length) return translate; | |
| translate = _; | |
| return tile; | |
| }; | |
| tile.zoomDelta = function(_) { | |
| if (!arguments.length) return zoomDelta; | |
| zoomDelta = +_; | |
| return tile; | |
| }; | |
| return tile; | |
| }; |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .stroke { | |
| fill: none; | |
| stroke: #000; | |
| stroke-width: .5; | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="//d3js.org/topojson.v1.min.js"></script> | |
| <script src="d3.geo.tile.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| var projection = d3.geo.mercator() | |
| .center([-96, 38.3]) | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| var tile = d3.geo.tile() | |
| .size([width, height]) | |
| .scale(projection.scale() * 2 * Math.PI) | |
| .translate(projection([0, 0])) | |
| .zoomDelta((window.devicePixelRatio || 1) - .5); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("/mbostock/raw/4090846/us.json", function(error, topology) { | |
| if (error) throw error; | |
| var tiles = tile(); | |
| var defs = svg.append("defs"); | |
| defs.append("path") | |
| .attr("id", "land") | |
| .datum(topojson.feature(topology, topology.objects.land)) | |
| .attr("d", path); | |
| defs.append("clipPath") | |
| .attr("id", "clip") | |
| .append("use") | |
| .attr("xlink:href", "#land"); | |
| svg.append("g") | |
| .attr("clip-path", "url(#clip)") | |
| .selectAll("image") | |
| .data(tiles) | |
| .enter().append("image") | |
| .attr("xlink:href", function(d) { return "http://" + ["a", "b", "c", "d"][Math.random() * 4 | 0] + ".tiles.mapbox.com/v3/mapbox.natural-earth-2/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; }) | |
| .attr("width", Math.round(tiles.scale)) | |
| .attr("height", Math.round(tiles.scale)) | |
| .attr("x", function(d) { return Math.round((d[0] + tiles.translate[0]) * tiles.scale); }) | |
| .attr("y", function(d) { return Math.round((d[1] + tiles.translate[1]) * tiles.scale); }); | |
| svg.append("use") | |
| .attr("xlink:href", "#land") | |
| .attr("class", "stroke"); | |
| }); | |
| </script> |
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