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Added an example that shows how to display a GeoJSON map inside a bro…
…wser (test/index.html).
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,166 @@ | ||
| /* eslint-disable one-var, semi-style, no-underscore-dangle, prefer-destructuring */ | ||
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| const SVG = (function() { | ||
| // | ||
| // -- Private Functions ------------------------------------------------------ | ||
|
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| /** | ||
| * Applies a mirror projection. | ||
| */ | ||
| function _mirror(coord, mirror) { | ||
| let c = []; | ||
|
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| switch (mirror) { | ||
| case 'x': | ||
| c[0] = coord[0]; | ||
| c[1] = -coord[1]; | ||
| break; | ||
|
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| case 'y': | ||
| c[0] = -coord[0]; | ||
| c[1] = coord[1]; | ||
| break; | ||
|
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| case 'xy': | ||
| c[0] = -coord[0]; | ||
| c[1] = -coord[1]; | ||
| break; | ||
|
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| default: | ||
| c = [...coord]; | ||
| } | ||
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| return c; | ||
| } | ||
|
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| /** | ||
| * Applies a mercator projection. | ||
| */ | ||
| function _mercator(φdegree, λdegree, zoom, λodegree) { | ||
| const z = zoom || 1 | ||
| , r = Math.PI / 180 | ||
| , φ = φdegree * r | ||
| // , λ = λdegree * r | ||
| , λo = λodegree || 0 | ||
| ; | ||
|
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| // let x = λ - λo; | ||
| // x /= r; | ||
| const x = λdegree - λo; | ||
| // A mercator projection for a latitude greater than 85.05° or lower | ||
| // than -85.05° tends to infinity. Thus, we limit the latitude | ||
| // to |85.05°| i.e., a projection to |180|. | ||
| let y; | ||
| if (φdegree > 85.05) { | ||
| y = 180; | ||
| } else if (φdegree < -85.05) { | ||
| y = -180; | ||
| } else { | ||
| y = Math.log(Math.tan((1 / 4) * Math.PI + (1 / 2) * φ)) / r; | ||
| } | ||
| return [x * z, y * z]; | ||
| } | ||
|
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| /** | ||
| * Applies a linear projection. | ||
| */ | ||
| function _linear(φ, λ) { | ||
| return [λ, φ]; | ||
| } | ||
|
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| /** | ||
| * Applies the requested transformations. | ||
| */ | ||
| function _transform(coord, option) { | ||
| let c; | ||
|
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| // Projection | ||
| if (option && option.projection && option.projection === 'mercator') { | ||
| c = _mercator(coord[0], coord[1], 1, 0); | ||
| } else { | ||
| c = _linear(coord[0], coord[1]); | ||
| } | ||
|
|
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| // Mirroring | ||
| if (option && option.mirror) { | ||
| c = _mirror(c, option.mirror); | ||
| } | ||
|
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| // Scaling | ||
| if (option && option.scale && typeof option.scale === 'number' && option.scale > 1) { | ||
| c = [c[0] * option.scale, c[1] * option.scale]; | ||
| } | ||
| return c; | ||
| } | ||
|
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||
| /** | ||
| * Converts the coordinates to an SVG path. | ||
| */ | ||
| function _getSVGPath(coord, options) { | ||
| let path | ||
| , subpath | ||
| , x | ||
| , y | ||
| , i | ||
| , j | ||
| ; | ||
|
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||
| path = ''; | ||
| for (i = 0; i < coord.length; i++) { | ||
| subpath = ''; | ||
| for (j = 0; j < coord[i].length; j++) { | ||
| [x, y] = _transform(coord[i][j], options); | ||
| if (subpath === '') { | ||
| subpath = `M${x},${y}`; | ||
| } else { | ||
| subpath += `L${x},${y}`; | ||
| } | ||
| } | ||
| subpath += 'z'; | ||
| path += subpath; | ||
| } | ||
| return path; | ||
| } | ||
|
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||
| /** | ||
| * Converts a GEOJSON to an XML SVG string. | ||
| */ | ||
| function _process(json, options) { | ||
| // Add the header: | ||
| let s = [ | ||
| '<!-- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. -->\n', | ||
| '<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">\n', | ||
| ' <g transform="translate(0, 0) scale(1, 1)">\n', | ||
| ].join(''); | ||
|
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||
| // Add the SVG elements: | ||
| let d; | ||
| if (json.type === 'FeatureCollection') { | ||
| for (let i = 0; i < json.features.length; i++) { | ||
| d = _getSVGPath(json.features[i].geometry.coordinates, options); | ||
| s += ` <path id="" class="land" d="${d}"></path>\n`; | ||
| } | ||
| } else { | ||
| d = _getSVGPath(json.geometry.coordinates, options); | ||
| s += ` <path id="" class="land" d="${d}"></path>\n`; | ||
| } | ||
|
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| // Append the XML Footer: | ||
| s += ' </g>\n'; | ||
| s += '</svg>\n'; | ||
|
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| return s; | ||
| } | ||
|
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|
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| // -- Public ----------------------------------------------------------------- | ||
|
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| return { | ||
| /** | ||
| * Converts a GeoJSON to an XML SVG string. | ||
| */ | ||
| to(json, options) { | ||
| return _process(json, options); | ||
| }, | ||
| }; | ||
| }()); |