s2-tools/dist/proj4/parseCode.js

A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.

import { buildDatum } from './datum';
import { D2R, FT_TO_M, PRIME_MERIDIAN, US_FT_TO_M, deriveEccentricity, deriveSphere, } from './constants';
import { isWKTProjection, parseWKTProjection } from '../readers/wkt';
/**
 * Parse a proj4 string or object into a projection object
 * TODO: Support json objects that use the jsonScheme.ts file
 * @param code - a proj4 projection definition string or object
 * @param transformer - the transformer to build the projection state around
 * @returns - a projection object
 */
export function parseProj(code, transformer) {
    let params = {};
    if (typeof code === 'object')
        params = code;
    else if (code[0] === '+')
        params = parseProj4Str(code);
    else if (isWKTProjection(code))
        params = parseWKTProjection(code);
    else
        throw new Error(`Invalid projection string: ${code}`);
    // adjust params as needed
    deriveSphere(params);
    deriveEccentricity(params);
    params.lat1 = params.lat1 ?? params.lat0; // Lambert_Conformal_Conic_1SP, for example, needs this
    params.k0 = params.k ?? params.k0;
    buildDatum(params, transformer);
    // filter undefined values
    Object.keys(params).forEach((key) => {
        // @ts-expect-error - key is a string
        if (params[key] === undefined)
            delete params[key];
    });
    return params;
}
/**
 * Parse a proj4 string into a projection object
 * @param code - a proj4 projection definition string
 * @returns - a projection description object
 */
function parseProj4Str(code) {
    return code
        .split('+')
        .map((v) => v.trim())
        .filter((a) => a.length > 0)
        .reduce((res, a) => {
        const [key, value] = a.split('=');
        parseProj4StrKeyValue(res, key, value);
        return res;
    }, {});
}
/**
 * Modify a key/value pair in a proj4 string to match the CRS projection standard
 * @param res - a projection description object
 * @param key - a proj4 string key
 * @param value - a proj4 string value
 */
function parseProj4StrKeyValue(res, key, value) {
    // adjust key
    key = key.replace(/_([a-zA-Z0-9])/g, (_, letter) => letter.toUpperCase());
    if (key === 'proj')
        res.name = value;
    else if ([
        'alpha',
        'lat0',
        'lat1',
        'lat2',
        'latTs',
        'fromGreenwich',
        'long0',
        'long1',
        'long2',
        'longc',
    ].includes(key))
        res[key] =
            parseFloat(value) * D2R;
    else if (['lon0', 'lon1', 'lon2', 'lonc'].includes(key)) {
        const modKey = key.replace('n', 'ng');
        res[modKey] = parseFloat(value) * D2R;
    }
    else if (['ellps', 'datumCode'].includes(key))
        res[key] = value;
    else if (key === 'datum')
        res.datumCode = value;
    else if (['noDefs', 'noOff', 'noRot', 'noUoff', 'rA', 'utmSouth', 'approx'].includes(key))
        res[key] = true;
    else if (key === 'zone')
        res[key] = parseInt(value, 10);
    else if (key === 'units') {
        res.units = value;
        if (value === 'us-ft')
            res.toMeter = US_FT_TO_M;
        else if (value === 'ft')
            res.toMeter = FT_TO_M;
    }
    else if (key === 'nadgrids') {
        res.nadgrids = value;
        if (value === '@null')
            res.datumCode = 'none';
    }
    else if (key === 'pm') {
        const pm = PRIME_MERIDIAN[value] ?? 0;
        res.fromGreenwich = pm * D2R;
    }
    else if (key === 'towgs84' || key === 'datumParams') {
        res.datumParams = value.split(',').map((a) => parseFloat(a));
    }
    else if (key === 'axis') {
        const legalAxis = 'ewnsud';
        if (value.length === 3 &&
            legalAxis.indexOf(value.slice(0, 1)) !== -1 &&
            legalAxis.indexOf(value.slice(1, 2)) !== -1 &&
            legalAxis.indexOf(value.slice(2, 3)) !== -1) {
            res.axis = value;
        }
    }
    else if (key === 'r' || key === 'R') {
        res.a = res.b = parseFloat(value);
    }
    else if (key === 'gamma') {
        res.rectifiedGridAngle = parseFloat(value);
    }
    else if (key === 'sweep') {
        res.sweep = value === 'x' ? 'x' : 'y';
    }
    else if (!isNaN(value))
        // @ts-expect-error - key is a string in ProjectionParams
        res[key] = parseFloat(value);
    // @ts-expect-error - key is a string in ProjectionParams
    else
        res[key] = value;
}
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