README
jMaps
jMaps is a light Javascript API for reading Natural Earth's DB files. jMaps provides methods to extract data from the database and creates GeoJSON and XML SVG outputs.
Usage
Extract data and create a GeoJSON object
var jMaps = require('jmaps');
// Create the object
const jmap = jMaps();
// Load the Natural Earth database:
jmap.load('<path>, <ne_110m_admin_0_countries>')
// Get a collection of maps (FeatureCollection)
const maps = jmap.getCollection();
// Get a map (Feature)
const map = jmap.getFeature('feature number');
The GeoJSON
object looks like:
{
bbox: [ ... ],
type: 'FeatureCollection',
features: [
{ type: 'Feature', properties: [Object], geometry: [Object] },
...
{ type: 'Feature', properties: [Object], geometry: [Object] }
]
}
A Feature
looks like:
{
type: 'Feature',
properties: { ... },
geometry : {
type: 'Polygon'
coordinates: [ ... ]
}
Nota:
A Natural Earth
's database is a folder that contains, at least, two files having the same name as the folder and with the suffix .dbf
and .shp
. For instance, Natural Earth
's database ne_50m_admin_0_countries
must contains the two files: ne_50m_admin_0_countries.dbf
and ne_50m_admin_0_countries.shp
.
Create an XML SVG file
const fs = require('fs');
const jMaps = require('jmaps');
const jmap = jMaps();
jmap.load('<path>, <ne_110m_admin_0_countries>')
// Transform the longitudes and latitudes, from a collection, to x, y plane coordinates
const map = jmap.transform({scale: 1, projection: 'mercator', mirror: 'x'});
// Create a File stream
const fd = fs.createWriteStream('path/to/svg/file', {flags: 'w'});
// Fill the write stream
jmap.toSVG(map, fs);
It creates an XML file that looks like:
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<g transform="translate(0, 0) scale(1, 1)">
<path id="" class="land" d="...."></path>
</g>
</svg>
A Feature
produces an XML SVG file with one path
while a FeatureCollection
produces an XML SVG file with a multitude of paths
.
You can enrich your XML files with information extracted from the property properties
of a Feature
object.
API
This module implements four methods:
- getFeature(
feature number
), - getCollection(),
- transform(
options
), - toSVG(
GeoJSON object
,write file stream
).
getFeature(n)
This method extracts one Feature
from Natural Earth
's database and returns a Javascript GeoJSON object.
This method requires one argument. Its is a number
- the Feature number. It starts from 1.
getCollection()
This method extracts a FeatureCollection
from Natural Earth
's database and returns a Javascript GeoJSON object. A FeatureCollection
is a set of Feature
.
transform(options)
This methods converts the longitude and latitude coordinates of the GeoJSON object to x, y plane coordinates. It returns the transformed Javascript GeoJSON object.
This methods extracts a collection from the loaded database, converts it and returns the converted GeoJSON object.
The options
argument is optional. If nothing is provided, the default options are:
{ scale: 1, projection: none, mirror: 'none' }
scale
can be any number from 1 to 'infinity'.
projection
can be none
or mercator
.
mirror
can be none
, x
, y
, xy
.
toSVG(GeoJSON, fd)
This method generates XML SVG data from a collection or a transformed collection.
This method requires two arguments. A GeoJSON
object (collection) and fd
, a file write stream handler.
License
MIT.