This variation of the map zooming example uses interaction to control a smooth zooming interpolator. Mouse over the map to zoom between San Francisco, New Orleans and New York.
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Map Zooming III
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| canvas { | |
| -webkit-tap-highlight-color: rgba(0,0,0,0); | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="//d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| // This projection is baked into the TopoJSON file, | |
| // but is used here to compute the desired zoom translate. | |
| var projection = d3.geo.mercator() | |
| .translate([0, 0]) | |
| .scale(4000); | |
| var zoom = d3.scale.linear() | |
| .domain([0, width / 2, width]) | |
| .range([ | |
| projection([-122.417, 37.775]).concat(width / 6), | |
| projection([-90.0500, 29.9667]).concat(width / 3), | |
| projection([-74.0064, 40.7142]).concat(width / 4) | |
| ]) | |
| .interpolate(d3.interpolateZoom); | |
| var scale, | |
| translate, | |
| area; // minimum area threshold for simplification | |
| var clip = d3.geo.clipExtent() | |
| .extent([[0, 0], [width, height]]); | |
| var simplify = d3.geo.transform({ | |
| point: function(x, y, z) { | |
| if (z >= area) this.stream.point(x * scale + translate[0], y * scale + translate[1]); | |
| } | |
| }); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .on("mousemove", mousemoved) | |
| .on("touchmove", touchmoved); | |
| var context = canvas.node().getContext("2d"); | |
| var path = d3.geo.path() | |
| .projection({stream: function(s) { return simplify.stream(clip.stream(s)); }}) | |
| .context(context); | |
| d3.json("us-states.json", function(error, json) { | |
| if (error) throw error; | |
| canvas.datum(topojson.mesh(topojson.presimplify(json))); | |
| render(0); | |
| }); | |
| function touchmoved() { | |
| render(d3.touches(this)[0][0]); | |
| d3.event.preventDefault(); | |
| } | |
| function mousemoved() { | |
| render(d3.mouse(this)[0]); | |
| } | |
| function render(x) { | |
| var point = zoom(x); | |
| scale = width / point[2]; | |
| translate = [width / 2 - point[0] * scale, height / 2 - point[1] * scale]; | |
| area = 1 / scale / scale; | |
| context.clearRect(0, 0, width, height); | |
| context.beginPath(); | |
| canvas.each(path); | |
| context.stroke(); | |
| } | |
| </script> |
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