geojson2svg

geojson2svg

Converts geojson to svg string given svg viewport size and maps extent. Check world map and color coded map examples to demostrate that its very easy to convert geojson into map.

Installation

Using in node.js or with browserify

npm install geojson2svg

For including in html page standard way, download file dist/geojson2svg.min.js

<script type="text/javascipt" src="path/to/geojson2svg.min.js"></script>

This creates a global variable 'geojson2svg'

geojson2svg is also available on cdnjs and can be included like:

<script type="text/javascipt" src="//cdnjs.cloudflare.com/ajax/libs/geojson2svg/x.x.x/geojson2svg.min.js"></script>

Usage

Using in node.js or with browserify

var geojson2svg = require('geojson2svg');
var converter = geojson2svg(options);
var svgString = converter.convert(geojson,options);

Using in browser standard way

var converter = geojson2svg(options);
var svgString = converter.convert(geojson,options);

convert function returns array of svg element string

Options

• viewportSize is object containing width and height in pixels. Default viewportSize values are:

  {
    width: 256,
    height: 256
  }

• mapExtent: {"left": coordinate, "bottom": coordinate, "right": coordinate, "top": coordinate}. Coordinates should be in same projection as of geojson. Default maps extent are of Web Mercator projection (EPSG:3857). Default extent values are:

  {
    left: -20037508.342789244,
    right: 20037508.342789244,
    bottom: -20037508.342789244,
    top: 20037508.342789244
  }

• output: 'svg'|'path' default is 'svg'

  'svg' - svg element string is returned like '<path d="M0,0 20,10 106,40"/>'

  'path' - path 'd' value is returned 'M0,0 20,10 106,40' a linestring

• fitTo 'width' | 'height' Fit ouput svg map to width or height.

• explode: true | false, default is false. Should multigeojson be exploded to many svg elements or not.

• attributes: Attributes which are required to attach as SVG attributes from features can be passed here as list of path in feature, like

  {"attributes": ["properties.foo", "properties.bar"]}

  output svg string would be:

  <path foo="fooVal-1" bar="barVal-1" d="M0,0 20,10 106,40"/>

  Note: If a feature does not have value at the mentioned path then the attribute key would not be attached to svg string and even error would not be thrown.

  In case attribute(s) need be attach to all SVG string, a json object containing attribute(key) and values(value) can be passed. If option is like

  {"attributes": {"class": "mapstyle"}}

  returned string would be

  '<path class="mapstyle" d="M0,0 20,10 106,40"/>'

• pointAsCircle: true | false, default is false. For point geojson return circle element for option: { "pointAsCircel": true } output svg string would be:

  '<cirlce cx="30" cy="40" r="1" />'

• r: radius of point svg element

• callback: function, accept function that will be called on every geojson conversion with output string as one input variable e.g:

  { "callback": function(svgString) {
    // do something with svgString
  }}
  

  Callback function could be used to render SVG string.

The options 'attributes', 'r' and 'callback' can also be given in convert function

var svgString = convertor.convert(geojson, 
  {
    "attributes": ...,
    "r": ...,
    "callback": function
  }

mapExtent is critical option default are the extents of Web Mercator projection ('EPSG:3857') or also known as Spherical Mercator. This projection is used by many web mapping sites (Google / Bing / OpenStreetMap). In case your source data is in geographic coordinates, it can be converted on the fly to Web Mercator Projection using reproject-spherical-mercator or reproject or proj4js. Check my world map example for detail.

Assigning id to SVG path

There are three ways for doing this. First and second, .converter reads it from feature.properties.id or feature.id. Third way, pass id along with attributes like converter.convert(feature, {attributes: {id:'foo-1', class: 'bar'}}). Preference order is first as id key in attributes then feature.id and last feature.properties.id.

Examples

Converts geojson LineString to svg element string:

var converter = geojson2svg(
  {
    viewportSize: {width: 200, height: 100},
    mapExtent: {left: -180, bottom: -90, right: 180, top: 90},
    output: 'svg' 
  }
);
var svgString = converter.convert(
  {type:'LineString',coordinates:[[10,10],[15,20],[30,10]]}
);
//svgString: ['<path d="M105.55555555555556,44.44444444444444 108.33333333333333,38.888888888888886 116.66666666666666,44.44444444444444" />']

Converts geojson Polygon to svg path data 'd' string:

var converter = geojson2svg(
  {
    viewportExtent: {width: 200, height: 100}, 
    mapExtent: {left: -180, bottom: -90, right: 180, top: 90},
    output: 'path'
  }
);
var pathData = converter.convert(
  {
    "type": "Polygon", 
    "coordinates": [
      [[30, 10], [40, 40], [20, 40], [10, 20], [30, 10]] 
    ]
  }
);
// pathData: ['M116.66666666666666,44.44444444444444 122.22222222222221,27.77777777777778 111.11111111111111,27.77777777777778 105.55555555555556,38.888888888888886 116.66666666666666,44.44444444444444Z']

Check my blog maps-on-blackboard for more detailed examples.

Developing

Once you run

npm install

then for running test

npm run test

to create build

npm run build

##License This project is licensed under the terms of the MIT license.

Changelog

v1.1.0

5 May 2017

• attributes option enhanced 77f4365
• Dist created 3b4152d