60 lines
1.8 KiB
JavaScript
60 lines
1.8 KiB
JavaScript
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import {geoEquirectangular, geoOrthographic} from "d3-geo";
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import {asin, atan, degrees, radians, sin, tan} from "./math";
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function gilbertForward(point) {
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return [point[0] / 2, asin(tan(point[1] / 2 * radians)) * degrees];
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}
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function gilbertInvert(point) {
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return [point[0] * 2, 2 * atan(sin(point[1] * radians)) * degrees];
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}
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export default function(projectionType) {
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if (projectionType == null) projectionType = geoOrthographic;
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var projection = projectionType(),
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equirectangular = geoEquirectangular().scale(degrees).precision(0).clipAngle(null).translate([0, 0]); // antimeridian cutting
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function gilbert(point) {
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return projection(gilbertForward(point));
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}
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if (projection.invert) gilbert.invert = function(point) {
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return gilbertInvert(projection.invert(point));
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};
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gilbert.stream = function(stream) {
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var s1 = projection.stream(stream), s0 = equirectangular.stream({
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point: function(lambda, phi) { s1.point(lambda / 2, asin(tan(-phi / 2 * radians)) * degrees); },
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lineStart: function() { s1.lineStart(); },
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lineEnd: function() { s1.lineEnd(); },
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polygonStart: function() { s1.polygonStart(); },
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polygonEnd: function() { s1.polygonEnd(); }
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});
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s0.sphere = s1.sphere;
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return s0;
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};
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function property(name) {
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gilbert[name] = function(_) {
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return arguments.length ? (projection[name](_), gilbert) : projection[name]();
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};
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}
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gilbert.rotate = function(_) {
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return arguments.length ? (equirectangular.rotate(_), gilbert) : equirectangular.rotate();
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};
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gilbert.center = function(_) {
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return arguments.length ? (projection.center(gilbertForward(_)), gilbert) : gilbertInvert(projection.center());
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};
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property("clipAngle");
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property("clipExtent");
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property("scale");
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property("translate");
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property("precision");
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return gilbert
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.scale(249.5);
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}
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