gis-tools-ts
Version:
A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.
104 lines • 3.85 kB
JavaScript
import { BufferReader } from '..';
import { DataBaseFile } from './dbf';
import { ShapeFileReader } from './shp';
import { Transformer } from '../../proj4';
import { iterZipFolder } from '../../util';
export * from './dbf';
export * from './shp';
/**
* # Read a Shapefile from a Gzip folder.
*
* ## Description
* Assumes the input is an arraybuffer that is pointing to a collection of zip shapefile data.
*
* ## Usage
* ```ts
* import { shapefileFromGzip, LambertConformalConic, EPSG_9974 } from 'gis-tools-ts';
*
* const reader = await shapefileFromGzip(arrayBufferInput, [LambertConformalConic], { EPSG_9974 });
*
* for await (const feature of reader) {
* console.log(feature);
* }
* ```
* @param input - raw buffer of gzipped data (folder of shp, dbf, prj, and/or cpg)
* @param defs - optional array of ProjectionTransformDefinitions to insert
* @param epsgCodes - a record of EPSG codes to use for the transformer if needed
* @returns - a Shapefile
*/
export async function shapefileFromGzip(input, defs, epsgCodes) {
let encoding = 'utf8';
let transform = undefined;
let dbfReader = undefined;
let shpData = undefined;
for (const item of iterZipFolder(new Uint8Array(input))) {
if (item.filename.endsWith('cpg')) {
encoding = new TextDecoder('utf8').decode(await item.read());
}
else if (item.filename.endsWith('dbf')) {
const data = await item.read();
dbfReader = new DataBaseFile(new BufferReader(data.buffer), encoding);
}
else if (item.filename.endsWith('shp')) {
shpData = await item.read();
}
else if (item.filename.endsWith('prj')) {
const data = await item.read();
transform = new Transformer();
if (defs !== undefined)
for (const def of defs)
transform.insertDefinition(def);
if (epsgCodes !== undefined)
for (const [key, value] of Object.entries(epsgCodes))
transform.insertEPSGCode(key, value);
transform.setSource(new TextDecoder('utf8').decode(data));
}
}
if (shpData === undefined)
throw new Error('Shapefile not found');
return new ShapeFileReader(new BufferReader(shpData.buffer), dbfReader, transform);
}
/**
* # Read a Shapefile from a URL.
*
* ## Description
* Assumes the input is pointing to shapefile data or a gzipped folder with .shp, .dbf, .prj, and/or .cpg
*
* ## Usage
* ```ts
* import { shapefileFromURL, LambertConformalConic, EPSG_9974 } from 'gis-tools-ts';
*
* const reader = await shapefileFromURL('https://example.com/data.zip', [LambertConformalConic], { EPSG_9974 });
*
* for await (const feature of reader) {
* console.log(feature);
* }
* ```
* @param url - the url to the shapefile
* @param defs - optional array of ProjectionTransformDefinitions to insert
* @param epsgCodes - a record of EPSG codes to use for the transformer if needed
* @returns - a Shapefile
*/
export async function shapefileFromURL(url, defs, epsgCodes) {
const data = await fetchShapefile(url);
if (url.endsWith('.zip'))
return shapefileFromGzip(data, defs, epsgCodes);
return new ShapeFileReader(new BufferReader(data));
}
/**
* Fetches a shapefile or gzipped folder
* @param url - the url to the shapefile
* @returns - raw data of a shapefile OR a gzipped folder that may include the dbf, prj, and/or cpg
*/
async function fetchShapefile(url) {
return await fetch(url)
.then(async (res) => {
if (!res.ok)
throw new Error(`Failed to fetch data from ${url}`);
return await res.arrayBuffer();
})
.catch((err) => {
throw new Error(`Failed to fetch data from ${url}: ${err}`);
});
}
//# sourceMappingURL=index.js.map