Uses a second canvas with different fill colors for each country to detect which country is highlighted.
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Selecting Countries on a Canvas Globe
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| background: #fcfcfa; | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 600, | |
| speed = 1e-2, | |
| start = Date.now(); | |
| var sphere = {type: "Sphere"}; | |
| var projection = d3.geo.orthographic() | |
| .scale(height / 2.1) | |
| .translate([width / 2, height / 2]) | |
| .clipAngle(90) | |
| .precision(.5); | |
| var graticule = d3.geo.graticule(); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var context = canvas.node().getContext("2d"); | |
| var path = d3.geo.path() | |
| .projection(projection) | |
| .context(context); | |
| var hiddenCanvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var hiddenContext = hiddenCanvas.node().getContext("2d"); | |
| var hiddenProjection = d3.geo.equirectangular() | |
| .translate([width / 2, height / 2]) | |
| .scale(width / 7); | |
| var hiddenPath = d3.geo.path() | |
| .projection(hiddenProjection) | |
| .context(hiddenContext); | |
| d3.json("world-110m.json", function(error, topo) { | |
| var selected = false; | |
| var land = topojson.feature(topo, topo.objects.land), | |
| borders = topojson.feature(topo, topo.objects.countries), | |
| grid = graticule(); | |
| var fillToCountry = {}; | |
| var i = borders.features.length; | |
| while (i--) { | |
| hiddenContext.beginPath(); | |
| hiddenPath(borders.features[i]); | |
| hiddenContext.fillStyle = "rgb(" + i + ",0,0)"; | |
| hiddenContext.fill(); | |
| } | |
| d3.timer(function() { | |
| projection.rotate([speed * (Date.now() - start), -15]); | |
| context.clearRect(0, 0, width, height); | |
| context.beginPath(); | |
| path(sphere); | |
| context.lineWidth = 3; | |
| context.strokeStyle = "#000"; | |
| context.stroke(); | |
| context.beginPath(); | |
| path(sphere); | |
| context.fillStyle = "#fff"; | |
| context.fill(); | |
| context.beginPath(); | |
| path(land); | |
| context.fillStyle = "#222"; | |
| context.fill(); | |
| context.beginPath(); | |
| path(borders); | |
| context.lineWidth = .5; | |
| context.strokeStyle = "#fff"; | |
| context.stroke(); | |
| context.beginPath(); | |
| path(grid); | |
| context.lineWidth = .5; | |
| context.strokeStyle = "rgba(119,119,119,.5)"; | |
| context.stroke(); | |
| if (selected !== false) { | |
| context.beginPath(); | |
| path(borders.features[selected]); | |
| context.fillStyle = "#0ad"; | |
| context.fill(); | |
| } | |
| }); | |
| canvas | |
| .on("mousemove", select) | |
| .on("touchstart", select); | |
| function select() { | |
| var pos = d3.mouse(this); | |
| var latlong = projection.invert(pos); | |
| var hiddenPos = hiddenProjection(latlong); | |
| if (hiddenPos[0] > -1) { | |
| var p = hiddenContext.getImageData(hiddenPos[0], hiddenPos[1], 1, 1).data; | |
| selected = p[0]; | |
| context.beginPath(); | |
| path(borders.features[selected]); | |
| context.fillStyle = "#0ad"; | |
| context.fill(); | |
| } else { | |
| selected = false; | |
| } | |
| }; | |
| }); | |
| d3.select(self.frameElement).style("height", (2*height) + "px"); | |
| </script> |
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