README.md

Based on the code for Crayon Map

drawnLayer

A canvas tile layer using OpenStreetMap data and Mapzen's vector tiles, to help you make colorful, custom-rendered maps. The coordinates of GeoJSON shapes are converted to relative pixel integers so you can draw them directly on canvas tiles.

Runs on Google Maps API and Leaflet maps.

Library includes GitHub's open source polyfill for fetch. Minified versions created by jsmin.

Leaflet Example

Suppose you wanted to draw shapes where OpenStreetMap returned landuse with kind=residential

var map = L.map('map');

// pass these values
L.drawnLayer('MAPZEN_KEY', 'landuse', function(geojson, canvasctx) {
  for (var f = 0; f < geojson.features.length; f++) {
    var feature = geojson.features[f];
    if (feature.properties.kind === 'residential') {
      CustomDrawFunction(feature.geometry, canvasctx);
    }
  }
}).addTo(map);

// your custom renderer
function CustomDrawFunction(geometry, canvasctx) {
  // only draw outer ring of polygons
  var coords = (geometry.type === 'Polygon') ? geometry.coordinates[0] : geometry.coordinates;

  // draw shape
  canvasctx.beginPath();
  canvasctx.moveTo(coords[0].x, coords[0].y);
  for (var pt = 1; pt < coords.length; pt++) {
    canvasctx.lineTo(coords[pt].x, coords[pt].y);
  }
  canvasctx.closePath();

  // fill in the shape
  canvasctx.fillStyle = 'darkgreen';
  canvasctx.fill();

  // if you just wanted to draw an outline
  canvasctx.strokeStyle = 'darkgreen';
  canvasctx.stroke();
}

Google Maps Example

var map = new google.maps.Map(document.getElementById('map'), { ... });

// pass these values
var dl = new DrawnLayer('MAPZEN_KEY', 'TILE_LAYERS', function(geojson, canvasctx) {
  geojson.features.map(function(feature) {
    if (feature.properties.kind === 'residential') {
      CustomDrawFunction(feature.geometry, canvasctx);
    }
  });
});
map.overlayMapTypes.insertAt(1, dl);

function CustomDrawFunction(geometry, canvasctx) {
  ... (see Leaflet example)
}

License

Open source, MIT license