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geojson.js
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geojson.js
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// Copyright (c) 2015 - 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// Replacement for the external assert method to reduce bundle size
// Since GeoJSON format issues are common to users we do show messages in
// this case
export default function assert(condition, message) {
if (!condition) {
throw new Error(`deck.gl: ${message}`);
}
}
/**
* "Normalizes" complete or partial GeoJSON data into iterable list of features
* Can accept GeoJSON geometry or "Feature", "FeatureCollection" in addition
* to plain arrays and iterables.
* Works by extracting the feature array or wrapping single objects in an array,
* so that subsequent code can simply iterate over features.
*
* @param {object} geojson - geojson data
* @param {Object|Array} data - geojson object (FeatureCollection, Feature or
* Geometry) or array of features
* @return {Array|"iteratable"} - iterable list of features
*/
export function getGeojsonFeatures(geojson) {
// If array, assume this is a list of features
if (Array.isArray(geojson)) {
return geojson;
}
assert(geojson.type, 'GeoJSON does not have type');
switch (geojson.type) {
case 'Feature':
// Wrap the feature in a 'Features' array
return [geojson];
case 'FeatureCollection':
// Just return the 'Features' array from the collection
assert(Array.isArray(geojson.features), 'GeoJSON does not have features array');
return geojson.features;
default:
// Assume it's a geometry, we'll check type in separateGeojsonFeatures
// Wrap the geometry object in a 'Feature' object and wrap in an array
return [{geometry: geojson}];
}
}
// Linearize
export function separateGeojsonFeatures(features, dataRange = {}) {
const separated = {
pointFeatures: [],
lineFeatures: [],
polygonFeatures: [],
polygonOutlineFeatures: []
};
const {startRow = 0, endRow = features.length} = dataRange;
for (let featureIndex = startRow; featureIndex < endRow; featureIndex++) {
const feature = features[featureIndex];
assert(feature && feature.geometry, 'GeoJSON does not have geometry');
const {geometry} = feature;
const sourceFeature = {
feature,
index: featureIndex
};
if (geometry.type === 'GeometryCollection') {
assert(Array.isArray(geometry.geometries), 'GeoJSON does not have geometries array');
const {geometries} = geometry;
for (let i = 0; i < geometries.length; i++) {
const subGeometry = geometries[i];
separateGeometry(subGeometry, separated, sourceFeature);
}
} else {
separateGeometry(geometry, separated, sourceFeature);
}
}
return separated;
}
function separateGeometry(geometry, separated, sourceFeature) {
const {type, coordinates} = geometry;
const {pointFeatures, lineFeatures, polygonFeatures, polygonOutlineFeatures} = separated;
checkCoordinates(type, coordinates);
// Split each feature, but keep track of the source feature and index (for Multi* geometries)
switch (type) {
case 'Point':
pointFeatures.push({
geometry,
sourceFeature
});
break;
case 'MultiPoint':
coordinates.forEach(point => {
pointFeatures.push({
geometry: {type: 'Point', coordinates: point},
sourceFeature
});
});
break;
case 'LineString':
lineFeatures.push({
geometry,
sourceFeature
});
break;
case 'MultiLineString':
// Break multilinestrings into multiple lines
coordinates.forEach(path => {
lineFeatures.push({
geometry: {type: 'LineString', coordinates: path},
sourceFeature
});
});
break;
case 'Polygon':
polygonFeatures.push({
geometry,
sourceFeature
});
// Break polygon into multiple lines
coordinates.forEach(path => {
polygonOutlineFeatures.push({
geometry: {type: 'LineString', coordinates: path},
sourceFeature
});
});
break;
case 'MultiPolygon':
// Break multipolygons into multiple polygons
coordinates.forEach(polygon => {
polygonFeatures.push({
geometry: {type: 'Polygon', coordinates: polygon},
sourceFeature
});
// Break polygon into multiple lines
polygon.forEach(path => {
polygonOutlineFeatures.push({
geometry: {type: 'LineString', coordinates: path},
sourceFeature
});
});
});
break;
default:
}
}
/**
* Returns the source feature that was passed to `separateGeojsonFeatures`
*/
export function unwrapSourceFeature(wrappedFeature) {
// The feature provided by the user is under `sourceFeature.feature`
return wrappedFeature.sourceFeature.feature;
}
/**
* Returns the index of the source feature that was passed to `separateGeojsonFeatures`
*/
export function unwrapSourceFeatureIndex(wrappedFeature) {
// The index of the feature provided by the user is under `sourceFeature.index`
return wrappedFeature.sourceFeature.index;
}
/**
* Simple GeoJSON validation util. For perf reasons we do not validate against the full spec,
* only the following:
- geometry.type is supported
- geometry.coordinate has correct nesting level
*/
const COORDINATE_NEST_LEVEL = {
Point: 1,
MultiPoint: 2,
LineString: 2,
MultiLineString: 3,
Polygon: 3,
MultiPolygon: 4
};
function checkCoordinates(type, coordinates) {
let nestLevel = COORDINATE_NEST_LEVEL[type];
assert(nestLevel, `Unknown GeoJSON type ${type}`);
while (coordinates && --nestLevel > 0) {
coordinates = coordinates[0];
}
assert(coordinates && Number.isFinite(coordinates[0]), `${type} coordinates are malformed`);
}