mirror of https://gitee.com/antv-l7/antv-l7
53 lines
1.3 KiB
JavaScript
53 lines
1.3 KiB
JavaScript
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var geojsonArea = require('@mapbox/geojson-area');
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module.exports = rewind;
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function rewind(gj, outer) {
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switch ((gj && gj.type) || null) {
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case 'FeatureCollection':
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gj.features = gj.features.map(curryOuter(rewind, outer));
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return gj;
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case 'GeometryCollection':
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gj.geometries = gj.geometries.map(curryOuter(rewind, outer));
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return gj;
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case 'Feature':
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gj.geometry = rewind(gj.geometry, outer);
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return gj;
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case 'Polygon':
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case 'MultiPolygon':
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return correct(gj, outer);
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default:
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return gj;
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}
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}
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function curryOuter(a, b) {
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return function(_) { return a(_, b); };
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}
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function correct(_, outer) {
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if (_.type === 'Polygon') {
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_.coordinates = correctRings(_.coordinates, outer);
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} else if (_.type === 'MultiPolygon') {
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_.coordinates = _.coordinates.map(curryOuter(correctRings, outer));
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}
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return _;
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}
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function correctRings(_, outer) {
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outer = !!outer;
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_[0] = wind(_[0], outer);
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for (var i = 1; i < _.length; i++) {
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_[i] = wind(_[i], !outer);
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}
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return _;
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}
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function wind(_, dir) {
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return cw(_) === dir ? _ : _.reverse();
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}
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function cw(_) {
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return geojsonArea.ring(_) >= 0;
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}
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