gdal-async

node-gdal-async

Read and write raster and vector geospatial datasets straight from Node.js with this native asynchrounous GDAL binding. To get started, browse the API Documentation or examples.

Fork Notes

This project is a fork of https://github.com/contra/node-gdal-next which is a fork of https://github.com/naturalatlas/node-gdal.

It adds a number of features, the main one being asynchronous operations.

• Support for asynchronous IO

Async support for vector data is currently experimental, with the following classses being async-compatible on master

• main open
• global Algorithms
• Dataset
• DatasetBands
• DatasetLayers
• Driver
• Geometry
• RasterBandPixels
• LayerFeatures

master is usually unit-tested and has all the working features universal-async is cutting edge for the vector async support vsimem has support for in-memory files - gdal.open supports opening a Buffer

Support for worker_threads is planned but it is not a priority project

Breaking Changes relative to node-gdal

• With PROJ 6+, the order of coordinates for EPSG geographic coordinate reference systems is latitude first, longitude second. If you don't want to make large code changes, you can replace code like gdal.SpatialReference.fromEPSG(4326) with gdal.SpatialReference.fromProj4('+init=epsg:4326')

Breaking Changes relative to node-gdal-next

• None, node-gdal-next is usually kept in sync

Installation

Pre-built binaries are provided for most recent Linux distributions, Windows 64 bit and OS X 10.15:

npm install gdal-async

By default all dependencies are the latest versions and bundled out of the box, but if you would like to link against a pre-installed gdal you will have to rebuild it when installing using the following flags:

# --shared_gdal allows linking to the OS-provided libgdal, requires libgdal-dev (debian: sudo apt-get install libgdal-dev)
$ npm install gdal-next --build-from-source --shared_gdal  

Sample Usage

Synchronous

Raster

const gdal = require("gdal-next")
const dataset = gdal.open("sample.tif")

console.log("number of bands: " + dataset.bands.count())
console.log("width: " + dataset.rasterSize.x)
console.log("height: " + dataset.rasterSize.y)
console.log("geotransform: " + dataset.geoTransform)
console.log("srs: " + (dataset.srs ? dataset.srs.toWKT() : 'null'))

Vector

const gdal = require("gdal-next")
const dataset = gdal.open("sample.shp")
const layer = dataset.layers.get(0)

console.log("number of features: " + layer.features.count())
console.log("fields: " + layer.fields.getNames())
console.log("extent: " + JSON.stringify(layer.extent))
console.log("srs: " + (layer.srs ? layer.srs.toWKT() : 'null'))

Asynchronous

Mixing of synchronous and asynchronous operations is supported.

Safe mixing of asynchronous operations

Simultaneous operations on distinct dataset objects are always safe and can run it parallel. Simultaneous operations on the same dataset object should be safe too but they won't run in parallel. This is a limitation of GDAL. The only way to have multiple parallel operations on the same file is to use multiple dataset objects. Keep in mind that Node/libuv won't be able to detect which async contexts are waiting on each other, so if you launch 16 simultaneous operations on 4 different datasets, there is always a chance that libuv will pick up 4 operations on the same dataset to run - which will take all 4 slots on the thread pool. It is recommended to either increase UV_THREADPOOL_SIZE or to make sure that every dataset has exactly one operation running at any given time.

Does not support worker_threads yet

With callbacks

If the last argument of an xxxAsync function is a callback, it will be called on completion with standard (e,r) semantics

In this case the function will return a resolved Promise

const gdal = require('../node-gdal-async') // Or where it is installed
gdal.openAsync('sample.tif', (e, dataset) => {
    dataset.bands.get(1).pixels.readAsync(0, 0, dataset.rasterSize.x,
        dataset.rasterSize.y, (e, data) => {
        if (e) {
            console.error(e);
            return;
        }
        console.log(data);
    });
});

With promises

If there is no callback, the function will return a Promise

gdal.openAsync('sample.tif').then((dataset) => {
    dataset.bands.get(1).pixels.readAsync(0, 0, dataset.rasterSize.x, dataset.rasterSize.y)
        .then((data) => {
            console.log(data);
        }).catch(e => console.error(e));
}).catch(e => console.error(e));

Bundled Drivers

AAIGrid, ACE2, ADRG, AIG, AVCBin, AVCE00, AeronavFAA, AirSAR, BLX, BMP, BNA, BT, CEOS, COASP, COSAR, CPG, CSV, CTG, CTable2, DGN, DIMAP, DIPEx, DOQ1, DOQ2, DTED, DXF, E00GRID, ECRGTOC, EDIGEO, EHdr, EIR, ELAS, ENVI, ERS, ESAT, ESRI Shapefile, MapInfo File, MBTiles, FAST, FIT, FujiBAS, GFF, GML, GPSBabel, GPSTrackMaker, GPX, GRASSASCIIGrid, GS7BG, GSAG, GSBG, GSC, GTX, GTiff, GenBin, GeoJSON, GeoRSS, Geoconcept, GPKG, HF2, HFA, HTF, IDA, ILWIS, INGR, IRIS, ISIS2, ISIS3, Idrisi, JAXAPALSAR, JDEM, JPEG, KMLSUPEROVERLAY, KML, KRO, L1B, LAN, LCP, LOSLAS, Leveller, MAP, MEM, MFF2, MFF, Memory, MVT, NDF, NGSGEOID, NITF, NTv2, NWT_GRC, NWT_GRD, OGR_GMT, OGR_PDS, OGR_SDTS, OGR_VRT, OSM, OpenAir, OpenFileGDB, PAux, PCIDSK, PDS, PGDUMP, PNG, PNM, REC, RMF, ROI_PAC, RPFTOC, RS2, RST, R, S57, SAGA, SAR_CEOS, SDTS, SEGUKOOA, SEGY, SGI, SNODAS, SQLite, SRP, SRTMHGT, SUA, SVG, SXF, TIL, TSX, Terragen, UK .NTF, USGSDEM, VICAR, VRT, WAsP, XPM, XPlane, XYZ, ZMap

Contributors

This binding was originally the product of a collaboration between Natural Atlas and Mapbox. Its contributors are Brandon Reavis, Brian Reavis, Dane Springmeyer, Zac McCormick, and others.

node-gdal-next is maintained by @contra

The async bindings are by @mmomtchev

Before submitting pull requests, please update the tests and make sure they all pass.

$ make test # test against bundled gdal
$ make test-shared # test against shared gdal

License

Copyright © 2015–2017 Natural Atlas, Inc. & Contributors

Copyright © 2020-2021 Momtchil Momtchev, @mmomtchev & Contributors

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.