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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 svgStrings = converter.convert(geojson,options);

Using in browser standard way

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

convert function returns array of svg element string

Now svg strings can be easily converted to HTML svg elements. Intentionally I have kept the geojson2svg's output as string to make it more modular. Here is simple way to convert svg strings to svg elements with parse-svg or with any other parser.

npm isntall parse-svg

or include in your html file

<script type="text/javascript" src="path/to/parse-svg.min.js"></script>

Simple way to convert svgStrings to svg elements

var parseSVG = require('parse-svg')
var svgElements = svgStrings.map(function(svgString) {
  return parseSVG(svgString)
})

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 or json object for static attributes, like shown here

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

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

    or static {"attributes": {"class": "mapstyle"}}

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

    or dynamic and static both

    {attributes: [
      {
        property: 'properties.foo',
        type: 'dynamic',
        key: 'id'
      }, {
        property: 'properties.baz',
        type: 'dynamic'
      }, {
        property: 'bar',
        value: 'barStatic',
        type: 'static'
      }]
    })
    

    output: [ '<path d="M128,128 128.00638801979818,127.99361198020182" id="fooVal-1" baz="bazVal-1" bar="barStatic"/>']

    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.

  • 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 svgStrings = 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 svgStrings = converter.convert(
  {type:'LineString',coordinates:[[10,10],[15,20],[30,10]]}
);
//svgStrings: ['<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.