@terrestris/ol-util/dist/ProjectionUtil/ProjectionUtil.js

A set of helper classes for working with openLayers

import _isNil from 'lodash';
import _isEmpty from 'lodash/isEmpty';
import _isString from 'lodash/isString';
import { register } from 'ol/proj/proj4';
import proj4 from 'proj4';
/**
 * Default proj4 CRS definitions.
 */
export const defaultProj4CrsDefinitions = [{
        crsCode: 'EPSG:25832',
        definition: '+proj=utm +zone=32 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs'
    },
    {
        crsCode: 'EPSG:31466',
        // eslint-disable-next-line
        definition: '+proj=tmerc +lat_0=0 +lon_0=6 +k=1 +x_0=2500000 +y_0=0 +ellps=bessel +towgs84=598.1,73.7,418.2,0.202,0.045,-2.455,6.7 +units=m +no_defs'
    }, {
        crsCode: 'EPSG:31467',
        // eslint-disable-next-line
        definition: '+proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0 +ellps=bessel +towgs84=598.1,73.7,418.2,0.202,0.045,-2.455,6.7 +units=m +no_defs'
    }];
/**
 * Default mappings for CRS identifiers (e.g. "urn:ogc:def:crs:EPSG::25832").
 */
export const defaultProj4CrsMappings = [{
        alias: 'urn:ogc:def:crs:EPSG::3857',
        mappedCode: 'EPSG:3857'
    }, {
        alias: 'urn:ogc:def:crs:EPSG::25832',
        mappedCode: 'EPSG:25832'
    }, {
        alias: 'urn:ogc:def:crs:EPSG::31466',
        mappedCode: 'EPSG:31466'
    }, {
        alias: 'urn:ogc:def:crs:EPSG::31467',
        mappedCode: 'EPSG:31467'
    }];
/**
 * Helper class for projection handling. Makes use of
 * [Proj4js](http://proj4js.org/).
 *
 * @class ProjectionUtil
 */
export class ProjectionUtil {
    /**
     * Registers custom CRS definitions to the application.
     *
     * @param { CrsDefinition | CrsDefinition[]} customCrsDefs The custom `proj4` definitions
     *   which should be registered additionally to default available CRS (s.
     *   `defaultProj4CrsDefinitions` above) as well.
     *   Further CRS definitions in proj4 format can be checked under
     *   http://epsg.io (e.g. http://epsg.io/3426.proj4).
     * @param {boolean} registerDefaults Whether the default CRS should be
     *   registered or not. Default is true.
     */
    static initProj4Definitions(customCrsDefs, registerDefaults = true) {
        let proj4CrsDefinitions = [];
        if (registerDefaults) {
            proj4CrsDefinitions = defaultProj4CrsDefinitions;
        }
        if (!_isNil(customCrsDefs) || customCrsDefs) {
            const crsDefs = Array.isArray(customCrsDefs) ?
                customCrsDefs : [customCrsDefs];
            crsDefs?.forEach(crsDef => {
                if (proj4CrsDefinitions?.findIndex(tCrs => tCrs.crsCode === crsDef?.crsCode) === -1) {
                    proj4CrsDefinitions.push(crsDef);
                }
            });
        }
        if (proj4CrsDefinitions?.length > 0) {
            proj4CrsDefinitions.forEach(crsDef => proj4.defs(crsDef.crsCode, crsDef.definition));
            register(proj4);
        }
    }
    /**
     * Registers custom CRS mappings to allow automatic CRS detection. Sometimes
     * FeatureCollections returned by the GeoServer may be associated with
     * CRS identifiers (e.g. "urn:ogc:def:crs:EPSG::25832") that aren't
     * supported by `proj4` and `OpenLayers` per default. Add appropriate
     * mappings to allow automatic CRS detection by `OpenLayers` here.
     *
     * @param {CrsMapping | CrsMapping[]} customCrsMappings The custom CRS mappings which will be
     *   added additionally to the by default available (s. `defaultProj4CrsMappings`
     *   above).
     * @param {boolean} useDefaultMappings Whether the default CRS should be mapped
     *   as well or not. Default is true.
     */
    static initProj4DefinitionMappings(customCrsMappings, useDefaultMappings = true) {
        let proj4CrsMappings = [];
        if (useDefaultMappings) {
            proj4CrsMappings = defaultProj4CrsMappings;
        }
        if (!_isEmpty(customCrsMappings)) {
            const crsMappings = Array.isArray(customCrsMappings) ?
                customCrsMappings : [customCrsMappings];
            crsMappings?.forEach(crsMapping => {
                if (proj4CrsMappings?.findIndex(mapping => mapping.alias === crsMapping?.alias) === -1) {
                    proj4CrsMappings.push(crsMapping);
                }
            });
        }
        proj4CrsMappings?.map(crsMapping => {
            const projDef = proj4.defs(crsMapping.mappedCode);
            proj4.defs(crsMapping.alias, projDef);
        });
    }
    /**
     * Converts geographic coordinates given in DDD format like `DD.DDDD°` to
     * the degree, minutes, decimal seconds (DMS) format like
     * `DDD° MM' SS.SSS"`.
     *
     * @param {number} value Value to be converted.
     *
     * @return {string} Converted value.
     */
    static toDms(value) {
        const deg = Math.floor(value);
        const min = Math.floor((value - deg) * 60);
        const sec = ((value - deg - min / 60) * 3600);
        return `${deg}° ${ProjectionUtil.zerofill(min)}' ${ProjectionUtil.zerofill(sec.toFixed(2))}''`;
    }
    /**
     * Converts geographic coordinates given in DDD format like `DD.DDDD°` to
     * the degree, decimal minutes (DMM) format like `DDD° MM.MMMM`.
     *
     * @param {number} value Value to be converted.
     *
     * @return {string} Converted value.
     */
    static toDmm(value) {
        const deg = Math.floor(value);
        const min = ((value - deg) * 60);
        return `${deg}° ${ProjectionUtil.zerofill(min.toFixed(4))}'`;
    }
    /**
     * Adds leading zero to all values less than 10 and returns this new
     * zerofilled value as String. Values which are greater than 10 are not
     * affected.
     *
     * @param {number|string} value Value to be zerofilled.
     *
     * @return {string} converted value with leading zero if necessary.
     */
    static zerofill(value) {
        const asNumber = _isString(value) ? parseFloat(value) : value;
        return asNumber < 10 ? `0${asNumber}` : `${asNumber}`;
    }
}
export default ProjectionUtil;
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