Node Mapnik

add_layer(new)

Add a new layer to this map

Parameters

clear

Remove all layers and styles from this map

clone

Clone this map object, returning a value which can be changed without mutating the original

Returns

font

Get all of the fonts currently registered as part of this map

Returns

fontDirectory

Get the currently-registered font directory, if any

Returns

fontFiles

Get all of the fonts currently registered as part of this map, as a mapping from font to font file

Returns

fromString(stylesheet, [options], callback)

Load styles, layers, and other information for this map from a Mapnik XML stylesheet given as a string.

Parameters

Example

var fs = require('fs');
map.fromString(fs.readFileSync('./style.xml', 'utf8'), function(err, res) {
  // details loaded
});

fromStringSync(stylesheet, [options])

Load styles, layers, and other information for this map from a Mapnik XML stylesheet given as a string.

Parameters

Example

var fs = require('fs');
map.fromStringSync(fs.readFileSync('./style.xml', 'utf8'));

get_layer(layer)

Get a layer out of this map, given a name or index

Parameters

Returns

Throws

• Error :

  if index is incorrect or layer is not found

layers

Get all of the currently-added layers in this map

Returns

load(stylesheet, [options], callback)

Load styles, layers, and other information for this map from a Mapnik XML stylesheet.

Parameters

loadFonts

Load fonts from local or external source

loadSync(stylesheet, [options])

Load styles, layers, and other information for this map from a Mapnik XML stylesheet.

Parameters

Example

map.loadSync('./style.xml');

queryMapPoint(x, y, [options], callback)

Query a Mapnik#Map object to retrieve layer and feature data based on an X and Y Mapnik#Map coordinates (use Map#queryPoint to query with geographic coordinates).

Parameters

Returns

Example

// iterate over the first layer returned and get all attribute information for each feature
map.queryMapPoint(10, 10, {layer: 0}, function(err, results) {
  if (err) throw err;
  console.log(results); // => [{"layer":"layer_name","featureset":{}}]
  var featureset = results[0].featureset;
  var attributes = [];
  var feature;
  while ((feature = featureset.next())) {
    attributes.push(feature.attributes());
  }
  console.log(attributes); // => [{"attr_key": "attr_value"}, {...}, {...}]
});

queryPoint(x, y, [options], callback)

Query a Mapnik#Map object to retrieve layer and feature data based on geographic coordinates of the source data (use Map#queryMapPoint to query with XY coordinates).

Parameters

Returns

Example

// query based on web mercator coordinates
map.queryMapPoint(-12957605.0331, 5518141.9452, {layer: 0}, function(err, results) {
  if (err) throw err;
  console.log(results); // => [{"layer":"layer_name","featureset":{}}]
  var featureset = results[0].featureset;
  var attributes = [];
  var feature;
  while ((feature = featureset.next())) {
    attributes.push(feature.attributes());
  }
  console.log(attributes); // => [{"attr_key": "attr_value"}, {...}, {...}]
});

render(renderable, [options])

Renders a mapnik object (image tile, grid, vector tile) by passing in a renderable mapnik object.

Parameters

Returns

Example

// render data to an image object
var map = new mapnik.Map(256, 256);
map.loadSync('./path/to/stylesheet.xml');
var image = new mapnik.Image(map.width, map.height);
map.render(image, {}, function(err, image) {
    if (err) throw err;
    console.log(image) // => mapnik image object with data from xml
});

// render data to a vector tile object
var map = new mapnik.Map(256, 256);
map.loadSync('./path/to/stylesheet.xml');
var vtile = new mapnik.VectorTile(9,112,195);
map.render(vtile, {}, function(err, vtile) {
    if (err) throw err;
    console.log(vtile); // => vector tile object with data from xml
});

resize(width, height)

Give this map new dimensions

Parameters

save(file)

Writes the map to an xml file

Parameters

Example

map.save("path/to/map.xml");

scale

Get the map's scale factor. This is the ratio between pixels and geographical units like meters.

Returns

scaleDenominator

Get the map's scale denominator.

Returns

toXML

Converts the map to an XML string

Example

var xml = map.toXML();

addData(buffer, [options], callback)

Add new vector tile data to an existing vector tile

Parameters

Example

var data_buffer = fs.readFileSync('./path/to/data.mvt'); // returns a buffer
var vt = new mapnik.VectorTile(9,112,195);
vt.addData(data_buffer, function(err) {
  if (err) throw err;
  // your custom code
});

addDataSync(buffer, [options])

Add raw data to this tile as a Buffer

Parameters

Example

var data_buffer = fs.readFileSync('./path/to/data.mvt'); // returns a buffer
// assumes you have created a vector tile object already
vt.addDataSync(data_buffer);
// your custom code

addGeoJSON(geojson, name, [options])

Add features to this tile from a GeoJSON string. GeoJSON coordinates must be in the WGS84 longitude & latitude CRS as specified in the GeoJSON Specification.

Parameters

Example

var geojson = { ... };
var vt = mapnik.VectorTile(0,0,0);
vt.addGeoJSON(JSON.stringify(geojson), 'layer-name', {});

addImage(image, name, [options])

Add a <mapnik.Image> as a tile layer (asynchronous)

Parameters

Example

var vt = new mapnik.VectorTile(1, 0, 0, {
  tile_size:256
});
var im = new mapnik.Image(256, 256);
vt.addImage(im, 'layer-name', {
  image_format: 'jpeg',
  image_scaling: 'gaussian'
}, function(err) {
  if (err) throw err;
  // your custom code using `vt`  
});

addImageBuffer(buffer, name, callback)

Add an encoded image buffer as a layer

Parameters

Example

var vt = new mapnik.VectorTile(1, 0, 0, {
  tile_size: 256
});
var image_buffer = fs.readFileSync('./path/to/image.jpg'); // returns a buffer
vt.addImageBufferSync(image_buffer, 'layer-name', function(err) {
  if (err) throw err;
  // your custom code
});

addImageBufferSync(buffer, name)

Add raw image buffer as a new tile layer (synchronous)

Parameters

Example

var vt = new mapnik.VectorTile(1, 0, 0, {
  tile_size: 256
});
var image_buffer = fs.readFileSync('./path/to/image.jpg');
vt.addImageBufferSync(image_buffer, 'layer-name');

addImageSync(image, name, options)

Add a Image as a tile layer (synchronous)

Parameters

Example

var vt = new mapnik.VectorTile(1, 0, 0, {
  tile_size:256
});
var im = new mapnik.Image(256, 256);
vt.addImageSync(im, 'layer-name', {
  image_format: 'jpeg',
  image_scaling: 'gaussian'
});

bufferedExtent

Get the extent including the buffer of this vector tile

Returns

Example

var vt = new mapnik.VectorTile(9,112,195);
var extent = vt.bufferedExtent();
console.log(extent); // [-11273544.4277, 4693845.0329, -11190380.9409, 4777008.5197];

clear(callback)

Remove all data from this vector tile

Parameters

Example

vt.clear(function(err) {
  if (err) throw err;
  console.log(vt.getData().length); // 0   
});

clearSync

Remove all data from this vector tile (synchronously)

Example

vt.clearSync();
console.log(vt.getData().length); // 0

composite(array, [options], callback)

Composite an array of vector tiles into one vector tile

Parameters

Example

var vt1 = new mapnik.VectorTile(0,0,0);
var vt2 = new mapnik.VectorTile(0,0,0);
var options = {
  scale: 1.0,
  offset_x: 0,
  offset_y: 0,
  area_threshold: 0.1,
  strictly_simple: false,
  multi_polygon_union: true,
  fill_type: mapnik.polygonFillType.nonZero,
  process_all_rings:false,
  scale_denominator: 0.0,
  reencode: true
}
// add vt2 to vt1 tile
vt1.composite([vt2], options, function(err) {
  if (err) throw err;
  // your custom code with `vt1`
});

compositeSync(array, [options])

Synchronous version of #VectorTile.composite

Parameters

Example

var vt1 = new mapnik.VectorTile(0,0,0);
var vt2 = new mapnik.VectorTile(0,0,0);
var options = { ... };
vt1.compositeSync([vt2], options);

empty

Return whether this vector tile is empty - whether it has no layers and no features

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var empty = vt.empty();
console.log(empty); // true

emptyLayers

Get the names of all of the empty layers in this vector tile

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var empty = vt.emptyLayers();
// assumes you have added data to your tile
console.log(empty); // ['layer-name', 'empty-layer']

extent

Get the extent of this vector tile

Returns

Example

var vt = new mapnik.VectorTile(9,112,195);
var extent = vt.extent();
console.log(extent); // [-11271098.44281895, 4696291.017841229, -11192826.925854929, 4774562.534805248]

getData([options], callback)

Get the data in this vector tile as a buffer (asynchronous)

Parameters

Example

vt.getData({
  compression: 'gzip',
  level: 9,
  strategy: 'FILTERED'
}, function(err, data) {
  if (err) throw err;
  console.log(data); // buffer
});

getDataSync([options])

Get the data in this vector tile as a buffer (synchronous)

Parameters

Returns

Example

var data = vt.getData({
  compression: 'gzip',
  level: 9,
  strategy: 'FILTERED'
});

info(buffer)

Return an object containing information about a vector tile buffer. Useful for debugging .mvt files with errors.

Parameters

Returns

Example

var buffer = fs.readFileSync('./path/to/tile.mvt');
var info = mapnik.VectorTile.info(buffer);
console.log(info);
// { layers: 
//   [ { name: 'world',
//      features: 1,
//      point_features: 0,
//      linestring_features: 0,
//      polygon_features: 1,
//      unknown_features: 0,
//      raster_features: 0,
//      version: 2 },
//    { name: 'world2',
//      features: 1,
//      point_features: 0,
//      linestring_features: 0,
//      polygon_features: 1,
//      unknown_features: 0,
//      raster_features: 0,
//      version: 2 } ],
//    errors: false }

layer(layer_name)

Extract the layer by a given name to a new vector tile

Parameters

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var data = fs.readFileSync('./path/to/data.mvt');
vt.addDataSync(data);
console.log(vt.names()); // ['layer-name', 'another-layer']
var vt2 = vt.layer('layer-name');
console.log(vt2.names()); // ['layer-name']

names

Get the names of all of the layers in this vector tile

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var data = fs.readFileSync('./path/to/data.mvt');
vt.addDataSync(data);
console.log(vt.names()); // ['layer-name', 'another-layer']

painted

Get whether the vector tile has been painted. "Painted" is a check to see if data exists in the source dataset in a tile.

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var painted = vt.painted();
console.log(painted); // false

paintedLayers

Get the names of all of the painted layers in this vector tile. "Painted" is a check to see if data exists in the source dataset in a tile.

Returns

Example

var vt = new mapnik.VectorTile(0,0,0);
var painted = vt.paintedLayers();
// assumes you have added data to your tile
console.log(painted); // ['layer-name']

query(longitude, latitude, [options], callback)

Query a vector tile by longitude and latitude and get an array of features in the vector tile that exist in relation to those coordinates.

A note on tolerance: If you provide a positive value for tolerance you are saying that you'd like features returned in the query results that might not exactly intersect with a given lon/lat. The higher the tolerance the slower the query will run because it will do more work by comparing your query lon/lat against more potential features. However, this is an important parameter because vector tile storage, by design, results in reduced precision of coordinates. The amount of precision loss depends on the zoom level of a given vector tile and how aggressively it was simplified during encoding. So if you want at least one match - say the closest single feature to your query lon/lat - is is not possible to know the smallest tolerance that will work without experimentation. In general be prepared to provide a high tolerance (1-100) for low zoom levels while you should be okay with a low tolerance (1-10) at higher zoom levels and with vector tiles that are storing less simplified geometries. The units tolerance should be expressed in depend on the coordinate system of the underlying data. In the case of vector tiles this is spherical mercator so the units are meters. For points any features will be returned that contain a point which is, by distance in meters, not greater than the tolerance value. For lines any features will be returned that have a segment which is, by distance in meters, not greater than the tolerance value. For polygons tolerance is not supported which means that your lon/lat must fall inside a feature's polygon otherwise that feature will not be matched.

Parameters

Returns

Example

vt.query(139.61, 37.17, {tolerance: 0}, function(err, features) {
  if (err) throw err;
  console.log(features); // array of objects
  console.log(features.length) // 1
  console.log(features[0].id()) // 89
  console.log(features[0].geometry().type()); // 'Polygon'
  console.log(features[0].distance); // 0
  console.log(features[0].layer); // 'layer name'
});

queryMany(array, options, [callback])

Query a vector tile by multiple sets of latitude/longitude pairs. Just like <mapnik.VectorTile.query> but with more points to search.

Parameters

Returns

Example

vt.queryMany([[139.61, 37.17], [140.64, 38.1]], {tolerance: 0}, function(err, results) {
  if (err) throw err;
  console.log(results.hits); // 
  console.log(results.features); // array of feature objects
  if (features.length) {
    console.log(results.features[0].layer); // 'layer-name'
    console.log(results.features[0].distance, features[0].x_hit, features[0].y_hit); // 0, 0, 0
  }
});

render(map, surface, [options], callback)

Render/write this vector tile to a surface/image, like a Image

Parameters

Example

var vt = new mapnik.VectorTile(0,0,0);
var tileSize = vt.tileSize;
var map = new mapnik.Map(tileSize, tileSize);
vt.render(map, new mapnik.Image(256,256), function(err, image) {
  if (err) throw err;   
  // save the rendered image to an existing image file somewhere
  // see mapnik.Image for available methods
  image.save('./path/to/image/file.png', 'png32');
});

reportGeometrySimplicity(callback)

Count the number of geometries that are not OGC simple

Parameters

Example

vectorTile.reportGeometrySimplicity(function(err, simple) {
  if (err) throw err;
  console.log(simple); // array of non-simple geometries and their layer info
  console.log(simple.length); // number
});

reportGeometrySimplicitySync

Count the number of geometries that are not OGC simple

Returns

Example

var simple = vectorTile.reportGeometrySimplicitySync();
console.log(simple); // array of non-simple geometries and their layer info
console.log(simple.length); // number

reportGeometryValidity([options], callback)

Count the number of geometries that are not OGC valid

Parameters

Example

vectorTile.reportGeometryValidity(function(err, valid) {
  console.log(valid); // array of invalid geometries and their layer info
  console.log(valid.length); // number    
});

reportGeometryValiditySync([options])

Count the number of geometries that are not OGC valid

Parameters

Returns

Example

var valid = vectorTile.reportGeometryValiditySync();
console.log(valid); // array of invalid geometries and their layer info
console.log(valid.length); // number

setData(buffer, [options], callback)

Replace the data in this vector tile with new raw data

Parameters

Example

var data = fs.readFileSync('./path/to/data.mvt');
vectorTile.setData(data, function(err) {
  if (err) throw err;
  // your custom code
});

setDataSync(buffer, [options])

Replace the data in this vector tile with new raw data (synchronous). This function validates geometry according to the Mapbox Vector Tile specification.

Parameters

Example

var data = fs.readFileSync('./path/to/data.mvt');
vectorTile.setDataSync(data);
// your custom code

toGeoJSON([layer], callback)

Get a GeoJSON representation of this tile

Parameters

Example

vectorTile.toGeoJSON(function(err, geojson) {
  if (err) throw err;
  console.log(geojson); // stringified GeoJSON
  console.log(JSON.parse(geojson)); // GeoJSON object
});

toGeoJSONSync([layer])

Syncronous version of VectorTile

Parameters

Returns

Example

var geojson = vectorTile.toGeoJSONSync();
geojson // stringified GeoJSON
JSON.parse(geojson); // GeoJSON object

toJSON([options])

Get a JSON representation of this tile

Parameters

Returns

Example

var vt = mapnik.VectorTile(10,131,242);
var buffer = fs.readFileSync('./path/to/data.mvt');
vt.setData(buffer);
var json = vectorTile.toJSON();
console.log(json); 
// { 
//   name: 'layer-name',
//   extent: 4096, 
//   version: 2,
//   features: [ ... ] // array of objects
// }

clear(callback)

Make this image transparent, removing all image data from it.

Parameters

Example

var img = new mapnik.Image(5,5);
img.fillSync(1);
console.log(img.getPixel(0, 0)); // 1
img.clear(function(err, result) {
  console.log(result.getPixel(0,0)); // 0
});

clearSync

Make this image transparent. (synchronous)

Example

var img = new mapnik.Image(5,5);
img.fillSync(1);
console.log(img.getPixel(0, 0)); // 1
img.clearSync();
console.log(img.getPixel(0, 0)); // 0

compare(image, [options])

Compare the pixels of one image to the pixels of another. Returns the number of pixels that are different. So, if the images are identical then it returns 0. And if the images share no common pixels it returns the total number of pixels in an image which is equivalent to im.width()*im.height().

Parameters

Returns

Example

// start with the exact same images
var img1 = new mapnik.Image(2,2);
var img2 = new mapnik.Image(2,2);
console.log(img1.compare(img2)); // 0

// change 1 pixel in img2
img2.setPixel(0,0, new mapnik.Color('green'));
console.log(img1.compare(img2)); // 1

// difference in color at first pixel
img1.setPixel(0,0, new mapnik.Color('red'));
console.log(img1.compare(img2)); // 1

// two pixels different
img2.setPixel(0,1, new mapnik.Color('red'));
console.log(img1.compare(img2)); // 2

// all pixels different
img2.setPixel(1,1, new mapnik.Color('blue'));
img2.setPixel(1,0, new mapnik.Color('blue'));
console.log(img1.compare(img2)); // 4

composite(image, [options], callback)

Overlay this image with another image, creating a layered composite as a new image

Parameters

Example

var img1 = new mapnik.Image.open('./path/to/image.png');
var img2 = new mapnik.Image.open('./path/to/another-image.png');
img1.composite(img2, {
  comp_op: mapnik.compositeOp['multiply'],
  dx: 0,
  dy: 0,
  opacity: 0.5,
  image_filters: 'invert agg-stack-blur(10,10)'
}, function(err, result) {
  if (err) throw err;
  // new image with `result`
});

copy(type, [options], callback)

Copy an image into a new image by creating a clone

Parameters

Example

var img = new mapnik.Image(4, 4, {type: mapnik.imageType.gray16});
var img2 = img.copy(mapnik.imageType.gray8, function(err, img2) {
  if (err) throw err;
  // custom code with `img2` converted into gray8 type
});

copySync(type, [options])

Copy an image into a new image by creating a clone

Parameters

Returns

Example

var img = new mapnik.Image(4, 4, {type: mapnik.imageType.gray16});
var img2 = img.copy(mapnik.imageType.gray8);
// custom code with `img2` as a gray8 type

data

Return a copy of the pixel data in this image as a buffer

Returns

Example

var img = new mapnik.Image.open('./path/to/image.png');
var buffr = img.data();

demultiply(callback)

Demultiply the pixels in this image, asynchronously. The opposite of premultiplying

Parameters

demultiplySync

Demultiply the pixels in this image. The opposite of premultiplying.

encode([format], [options], callback)

Encode this image into a buffer of encoded data

Parameters

Returns

Example

var img = new mapnik.Image.open('./path/to/image.png');
myImage.encode('png', function(err, encoded) {
  if (err) throw err;
  // write buffer to new file
  fs.writeFileSync('myimage.png', encoded);
});

// encoding an image object with a mapnik.Palette
var im = new mapnik.Image(256, 256);
var pal = new mapnik.Palette(new Buffer('\xff\x09\x93\xFF\x01\x02\x03\x04','ascii'));
im.encode('png', {palette: pal}, function(err, encode) {
  if (err) throw err;
  // your custom code with `encode` image buffer
});

encodeSync([format], [options])

Encode this image into a buffer of encoded data (synchronous)

Parameters

Returns

Example

var img = new mapnik.Image.open('./path/to/image.png');
var buffer = img.encodeSync('png');
// write buffer to a new file
fs.writeFileSync('myimage.png', buffer);

fill(color, callback)

Fill this image with a given color. Changes all pixel values.

Parameters

Example

var img = new mapnik.Image(5,5);
img.fill(new mapnik.Color('blue'), function(err, img) {
  if (err) throw err;
  var colors = img.getPixel(0,0, {get_color: true});
  pixel is colored blue
  console.log(color.b); // 255
});

// or fill with rgb string
img.fill('rgba(255,255,255,0)', function(err, img) { ... });

fillSync(color)

Fill this image with a given color. Changes all pixel values. (synchronous)

Parameters

Example

var img = new mapnik.Image(5,5);
// blue pixels
img.fillSync(new mapnik.Color('blue'));
var colors = img.getPixel(0,0, {get_color: true});
// blue value is filled
console.log(colors.b); // 255

filter(filter, callback)

Apply a filter to this image. Changes all pixel values.

Parameters

Example

var img = new mapnik.Image(5, 5);
img.filter('sobel', function(err, img) {
  if (err) throw err;
  // your custom `img` with sobel filter
  // https://en.wikipedia.org/wiki/Sobel_operator
});

filterSync(filter)

Apply a filter to this image. This changes all pixel values. (synchronous)

Parameters

Example

var img = new mapnik.Image(5, 5);
img.filter('blur');
// your custom code with `img` having blur applied

fromBytesSync(buffer)

Create an image from a byte stream buffer. (synchronous)

Parameters

Returns

Example

var buffer = fs.readFileSync('./path/to/image.png');
var img = new mapnik.Image.fromBytesSync(buffer);

getPixel(x, y, [options])

Get a specific pixel and its value

Parameters

Returns

Example

// check for color after rendering image
var img = new mapnik.Image(4, 4);
var map = new mapnik.Map(4, 4);
map.background = new mapnik.Color('green');
map.render(img, {},function(err, img) {
  console.log(img.painted()); // false
  var pixel = img.getPixel(0,0);
  var values = img.getPixel(0,0, {get_color: true});
  console.log(pixel); // 4278222848
  console.log(values); // { premultiplied: false, a: 255, b: 0, g: 128, r: 0 }
});

getType

Determine the image type

Returns

Example

var img = new mapnik.Image(256, 256, {
  type: mapnik.imageType.gray8
});
var type = img.getType();
var typeCheck = mapnik.imageType.gray8;
console.log(type, typeCheck); // 1, 1

height

Get this image's height in pixels

Returns

Example

var img = new mapnik.Image(4,4);
console.log(img.height()); // 4

isSolid

Test if an image's pixels are all exactly the same

Returns

Example

var img = new mapnik.Image(2,2);
console.log(img.isSolid()); // true

// change a pixel
img.setPixel(0,0, new mapnik.Color('green'));
console.log(img.isSolid()); // false

isSolidSync

Determine whether the image is solid - whether it has alpha values of greater than one.

Returns

Example

var img = new mapnik.Image(256, 256);
var view = img.view(0, 0, 256, 256);
console.log(view.isSolidSync()); // true

openSync(path)

Load in a pre-existing image as an image object

Parameters

Returns

Example

var img = new mapnik.Image.open('./path/to/image.jpg');

painted

Check if this image is painted. "Painted" refers to if it has data or not. An image created with new mapnik.Image(4,4) defaults to false since we loaded a new image without rendering and have no idea if it was painted or not. You can run new mapnik.Image(4, 4, {painted: true}) to manually set the painted value.

Returns

Example

var img = new mapnik.Image(5,5);
console.log(img.painted()); // false

premultiplied

Determine whether the given image is premultiplied. https://en.wikipedia.org/wiki/Alpha_compositing

Returns

Example

var img = new mapnik.Image(5,5);
console.log(img.premultiplied()); // false
img.premultiplySync()
console.log(img.premultiplied()); // true

premultiply(callback)

Premultiply the pixels in this image, asynchronously

Parameters

Example

var img = new mapnik.Image(5,5);
img.premultiply(function(err, img) {
  if (err) throw err;
  // your custom code with premultiplied img
})

premultiplySync

Premultiply the pixels in this image.

Example

var img = new mapnik.Image(5,5);
img.premultiplySync();
console.log(img.premultiplied()); // true

resize(width, height, [options], callback)

Resize this image (makes a copy)

Parameters

Example

var img = new mapnik.Image(4, 4, {type: mapnik.imageType.gray8});
img.resize(8, 8, function(err, result) {
  if (err) throw err;
  // new image object as `result`
});

resizeSync(width, height, [options])

Resize this image (makes a copy). Synchronous version of mapnik.Image.resize .

Parameters

Returns

Example

var img = new mapnik.Image(4, 4, {type: mapnik.imageType.gray8});
var img2 = img.resizeSync(8, 8);
// new copy as `img2`

save(filename, [format], callback)

Encode this image and save it to disk as a file.

Parameters

Example

img.save('image.png', 'png', function(err) {
  if (err) throw err;
  // your custom code
});

saveSync(filename, [format])

Encode this image and save it to disk as a file.

Parameters

Example

img.saveSync('foo.png');

setGrayScaleToAlpha(color)

Convert all grayscale values to alpha values. Great for creating a mask layer based on alpha values.

Parameters

Example

var image = new mapnik.Image(2,2);
image.fillSync(new mapnik.Color('rgba(0,0,0,255)'));
console.log(image.getPixel(0,0, {get_color:true})); // { premultiplied: false, a: 255, b: 0, g: 0, r: 0 }

image.setGrayScaleToAlpha();
// turns a black pixel into a completely transparent mask
console.log(image.getPixel(0,0, {get_color:true})); // { premultiplied: false, a: 0, b: 255, g: 255, r: 255 }

setPixel(x, y, numeric)

Set a pixels value

Parameters

Example

var gray = new mapnik.Image(256, 256);
gray.setPixel(0,0,new mapnik.Color('white'));
var pixel = gray.getPixel(0,0,{get_color:true});
console.log(pixel); // { premultiplied: false, a: 255, b: 255, g: 255, r: 255 }

view(x, y, width, height)

Get a constrained view of this image given x, y, width, height parameters.

Parameters

Returns

Example

var img = new mapnik.Image(10, 10);
// This function says "starting from the 0/0 pixel, grab 5 pixels along
// the x-axis and 5 along the y-axis" which gives us a quarter of the original
// 10x10 pixel image
var img2 = img.view(0, 0, 5, 5);
console.log(img.width(), img2.width()); // 10, 5

width

Get this image's width in pixels

Returns

Example

var img = new mapnik.Image(4,4);
console.log(img.width()); // 4

addField

Get all of this grid's fields

addField(field)

Add a field to this grid's output

Parameters

encodeSync([options])

Get a constrained view of this field given x, y, width, height parameters.

Parameters

Returns

height

Get this grid's height

Returns

view(x, y, width, height)

Get a constrained view of this field given x, y, width, height parameters.

Parameters

Returns

width

Get this grid's width

Returns

attributes

Get the feature's attributes as an object.

Returns

extent

Get the feature's extent

Returns

geometry

Get the feature's attributes as a Mapnik geometry.

Returns

id

Returns

toJSON

Generate and return a GeoJSON representation of this feature

Returns

get_premultiplied

Get whether this color is premultiplied

Returns

hex

Get this color represented as a hexademical string

Returns

Example

var c = new mapnik.Color('green');
c.hex();
// '#008000'

set_premultiplied(premultiplied)

Set whether this color should be premultiplied

Parameters

Throws

• TypeError :

  given a non-boolean argument

Example

var c = new mapnik.Color('green');
c.set_premultiplied(true);

toString

Get this color's representation as a string

Returns

Example

var green = new mapnik.Color('green');
green.toString()
// 'rgb(0,128,0)'

describe

Describe the datasource's contents and type.

Returns

extent

Get the Datasource's extent

Returns

featureset([options])

Get features from this dataset using an iterator.

Parameters

Returns

Example

var features = [];
var featureset = ds.featureset();
var feature;
while ((feature = featureset.next())) {
    features.push(feature);
}

fields

Get only the fields metadata from a dataset.

Returns

Example

var fields = ds.fields();
// {
//     FIPS: 'String',
//     ISO2: 'String',
//     ISO3: 'String',
//     UN: 'Number',
//     NAME: 'String',
//     AREA: 'Number',
//     POP2005: 'Number',
//     REGION: 'Number',
//     SUBREGION: 'Number',
//     LON: 'Number',
//     LAT: 'Number'
// }

extent

Get the geometry's extent

Returns

toJSON([options], callback)

Convert this geometry into a GeoJSON representation, asynchronously.

Parameters

toJSONSync

Convert this geometry into a GeoJSON representation, synchronously.

Returns

toWKB

Get the geometry's representation as Well-Known Binary

Returns

toWKT

Get the geometry's representation as Well-Known Text

Returns

type

Get the geometry type

Returns

typeName

Get the geometry's representation as a GeoJSON type

Returns

next

Return the next Feature in this featureset if it exists, or null if it does not.

Returns

forward(position)

Project from a position in WGS84 space to a position in this projection.

Parameters

Returns

Example

var merc = new mapnik.Projection('+init=epsg:3857');
var long_lat_coords = [-122.33517, 47.63752];
var projected = merc.forward(long_lat_coords);

inverse(position)

Unproject from a position in this projection to the same position in WGS84 space.

Parameters

Returns