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forked from loganwilliams's block: projection debugging
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April 17, 2019 21:00
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projection debugging
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| license: mit |
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| <!DOCTYPE html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <script src="https://d3js.org/d3.v5.min.js"></script> | |
| <style> | |
| body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; } | |
| </style> | |
| </head> | |
| <body> | |
| <canvas width=960 height=500> | |
| <script> | |
| let width = 960; | |
| let height = 500; | |
| let context = d3.select("canvas").node().getContext('2d'); | |
| let path1 = d3.geoPath(); | |
| let path2 = d3.geoPath(); | |
| const degrees = 180/Math.PI; | |
| let transform = (lng, lat) => { | |
| let x = d3.scaleLinear().domain([-180, 180]).range([0, width])(lng); | |
| let y = d3.scaleLinear().domain([-90, 90]).range([height, 0])(lat); | |
| return {x, y: y + x * 0.2 | |
| } | |
| }; | |
| let projection2 = d3.geoTransform({ | |
| point: function(x,y) { | |
| const t = transform(x, y); | |
| this.stream.point(t.x, t.y); | |
| } | |
| }); | |
| let projection1 = d3.geoProjection((x,y) => { | |
| const t = transform(x*degrees, y*degrees); | |
| return [t.x, -t.y]; | |
| }).scale(1) | |
| d3.json("world_countries.json").then(d => { | |
| path1.projection(projection1).context(context); | |
| context.strokeStyle = "#F00"; | |
| context.beginPath(); | |
| path1(d) | |
| context.stroke(); | |
| path2.projection(projection2).context(context); | |
| context.strokeStyle = "#00F"; | |
| context.beginPath(); | |
| path2(d) | |
| context.stroke(); | |
| }) | |
| </script> | |
| </body> |
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