Mapnik

src/node_mapnik.cpp

`mapnik`

Mapnik is the core of cartographic design and processing.

property type description

version string
current version of mapnik

module_path string
path to native mapnik binding

supports Object
indicates which of the following are supported: grid, svg, cairo, cairo_pdf, cairo_svg, png, jpeg, tiff, webp, proj4, threadsafe

versions Object
diagnostic object with versions of node, v8, boost, boost_number, mapnik, mapnik_number, mapnik_git_describe, cairo

property	type	description
version	`string`	current version of mapnik
module_path	`string`	path to native mapnik binding
supports	`Object`	indicates which of the following are supported: grid, svg, cairo, cairo_pdf, cairo_svg, png, jpeg, tiff, webp, proj4, threadsafe
versions	`Object`	diagnostic object with versions of node, v8, boost, boost_number, mapnik, mapnik_number, mapnik_git_describe, cairo

Examples

var mapnik = require('node-mapnik');

src/node_mapnik.cpp

`compositeOp`

Image type constants representing color and grayscale encodings. Composite operation constants

property type description

clear number

src number

dst number

src_over number

dst_over number

src_in number

dst_in number

src_out number

dst_out number

src_atop number

dst_atop number

xor number

plus number

minus number

multiply number

screen number

overlay number

darken number

lighten number

color_dodge number

color_burn number

hard_light number

soft_light number

difference number

exclusion number

contrast number

invert number

invert number
-rgb

grain_merge number

grain_extract number

hue number

saturation number

color number

linear_dodge number

linear_burn number

divide number

property	type	description
clear	`number`
src	`number`
dst	`number`
src_over	`number`
dst_over	`number`
src_in	`number`
dst_in	`number`
src_out	`number`
dst_out	`number`
src_atop	`number`
dst_atop	`number`
xor	`number`
plus	`number`
minus	`number`
multiply	`number`
screen	`number`
overlay	`number`
darken	`number`
lighten	`number`
color_dodge	`number`
color_burn	`number`
hard_light	`number`
soft_light	`number`
difference	`number`
exclusion	`number`
contrast	`number`
invert	`number`
invert	`number`	-rgb
grain_merge	`number`
grain_extract	`number`
hue	`number`
saturation	`number`
color	`number`
linear_dodge	`number`
linear_burn	`number`
divide	`number`

src/node_mapnik.cpp

`imageType`

Image type constants representing color and grayscale encodings.

property type description

rgba8 number

gray8 number

gray8s number

gray16 number

gray16s number

gray32 number

gray32s number

gray32f number

gray63 number

gray63s number

gray63f number

property	type	description
rgba8	`number`
gray8	`number`
gray8s	`number`
gray16	`number`
gray16s	`number`
gray32	`number`
gray32s	`number`
gray32f	`number`
gray63	`number`
gray63s	`number`
gray63f	`number`

src/mapnik_color.cpp

`mapnik.Color(value, green, blue, blue, premultiplied)`

parameter type description

value string or number
either an array of [r, g, b, a], a color keyword, or a CSS color in rgba() form.

green number

blue number

blue number

premultiplied boolean

parameter	type	description
value	`string` or `number`	either an array of [r, g, b, a], a color keyword, or a CSS color in rgba() form.
green	`number`
blue	`number`
blue	`number`
premultiplied	`boolean`

Throws

exception	description
`TypeError`	if a rgb component is outside of the 0-255 range

Examples

var c = new mapnik.Color('green');
var c = new mapnik.Color(0, 128, 0, 255);
// premultiplied
var c = new mapnik.Color(0, 128, 0, 255, true);

src/mapnik_color.cpp

`get_premultiplied`

Get whether this color is premultiplied

Returns

boolean :

premultiplied

src/mapnik_color.cpp

`hex`

Get this color represented as a hexademical string

Returns

string :

hex representation

Examples

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

src/mapnik_color.cpp

`set_premultiplied(premultiplied)`

Set whether this color should be premultiplied

parameter type description

premultiplied boolean

parameter	type	description
premultiplied	`boolean`

Throws

exception	description
`TypeError`	given a non-boolean argument

Examples

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

src/mapnik_color.cpp

`toString`

Get this color's representation as a string

Returns

string :

color as a string

Examples

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

src/mapnik_datasource.cpp

`mapnik.Datasource`

A Datasource object. This is the connector from Mapnik to any kind of file, network, or database source of geographical data.

src/mapnik_datasource.cpp

`describe`

Describe the datasource's contents and type.

Returns

Object :

description: an object with type, fields, encoding, geometry_type, and proj4 code

src/mapnik_datasource.cpp

`extent`

Get the Datasource's extent

Returns

Array<number> :

extent [minx, miny, maxx, maxy] order feature extent.

src/mapnik_feature.cpp

`mapnik.Feature`

A single geographic feature, with geometry and properties. This is typically derived from data by a datasource, but can be manually created.

src/mapnik_feature.cpp

`fromJSON(geojson)`

parameter type description

geojson string
string

Create a feature from a GeoJSON representation.

parameter	type	description
geojson	`string`	string Create a feature from a GeoJSON representation.

src/mapnik_feature.cpp

`attributes`

Get the feature's attributes as an object.

Returns

Object :

attributes

src/mapnik_feature.cpp

`extent`

Get the feature's extent

Returns

Array<number> :

extent [minx, miny, maxx, maxy] order feature extent.

src/mapnik_feature.cpp

`geometry`

Get the feature's attributes as a Mapnik geometry.

Returns

mapnik.Geometry :

geometry

src/mapnik_feature.cpp

`id`

Returns

number :

id the feature's internal id

src/mapnik_feature.cpp

`toJSON`

Generate and return a GeoJSON representation of this feature

Returns

string :

geojson Feature object in stringified GeoJSON

src/mapnik_featureset.cpp

`mapnik.Featureset`

An iterator of mapnik.Feature objects.

src/mapnik_featureset.cpp

`next`

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

Returns

mapnik.Feature or :

next feature

src/mapnik_geometry.cpp

`mapnik.Geometry`

Geometry: a representation of geographical features in terms of shape alone. This class provides many useful functions for conversion to and from formats.

You'll never create a mapnik.Geometry instance manually: it is always part of a mapnik.Feature instance, which is often a part of a mapnik.Featureset instance.

src/mapnik_geometry.cpp

`extent`

Get the geometry's extent

Returns

Array<number> :

extent [minx, miny, maxx, maxy] order geometry extent.

src/mapnik_geometry.cpp

`toJSON([options], callback)`

Convert this geometry into a GeoJSON representation, asynchronously.

parameter type description

options [Object] (default {})
. The only supported object is transform, which should be a valid mapnik.ProjTransform object.

callback Function
called with (err, result)

parameter	type	description
options	`[Object]` (default `{}`)	. The only supported object is `transform`, which should be a valid `mapnik.ProjTransform` object.
callback	`Function`	called with (err, result)

src/mapnik_geometry.cpp

`toJSONSync`

Convert this geometry into a GeoJSON representation, synchronously.

Returns

string :

GeoJSON, string-encoded representation of this geometry.

src/mapnik_geometry.cpp

`toWKB`

Get the geometry's representation as Well-Known Binary

Returns

string :

wkb representation of this geometry

src/mapnik_geometry.cpp

`toWKT`

Get the geometry's representation as Well-Known Text

Returns

string :

wkt representation of this geometry

src/mapnik_grid.cpp

`mapnik.Grid(width, height, [options])`

Generator for UTFGrid representations of data.

parameter type description

width number

height number

options [Object] (default {})
optional argument, which can have a 'key' property

parameter	type	description
width	`number`
height	`number`
options	`[Object]` (default `{}`)	optional argument, which can have a 'key' property

property type description

key string

property	type	description
key	`string`

src/mapnik_grid.cpp

`addField`

Get all of this grid's fields

Returns

Array<string> :

fields

src/mapnik_grid.cpp

`addField(field)`

Add a field to this grid's output

parameter type description

field string

parameter	type	description
field	`string`

src/mapnik_grid.cpp

`encodeSync([options])`

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

parameter type description

options [Object] (default { resolution: 4, features: false })

parameter	type	description
options	`[Object]` (default `{ resolution: 4, features: false }`)

Returns

Object :

an encoded field with grid, keys, and data members.

src/mapnik_grid.cpp

`height`

Get this grid's height

Returns

number :

height

src/mapnik_grid.cpp

`view(x, y, width, height)`

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

parameter type description

x number

y number

width number

height number

parameter	type	description
x	`number`
y	`number`
width	`number`
height	`number`

Returns

mapnik.Grid :

a grid constrained to this new view

src/mapnik_grid.cpp

`width`

Get this grid's width

Returns

number :

width

src/mapnik_image.cpp

`mapnik.Image(width, height, options)`

parameter type description

width number

height number

options Object
valid options are premultiplied, painted, type and initialize.

parameter	type	description
width	`number`
height	`number`
options	`Object`	valid options are `premultiplied`, `painted`, `type` and `initialize`.

Throws

exception	description
`TypeError`	if any argument is the wrong type, like if width or height is not numeric.

Examples

var im = new mapnik.Image(256, 256, {
  premultiplied: true,
  type: mapnik.imageType.gray8
});

src/mapnik_image.cpp

`fromBytes(buffer, callback)`

Create a new image from a buffer

parameter type description

buffer Buffer

callback Function

parameter	type	description
buffer	`Buffer`
callback	`Function`

src/mapnik_image.cpp

`clear(callback)`

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

parameter type description

callback Function

parameter	type	description
callback	`Function`

src/mapnik_image.cpp

`clearSync`

Make this image transparent.

Examples

var im = new mapnik.Image(5,5);
im.fillSync(1);
assert.equal(im.getPixel(0, 0), 1);
im.clearSync();
assert.equal(im.getPixel(0, 0), 0);

src/mapnik_image.cpp

`compare(other, [options])`

Compare two images visually. This is useful for algorithms and tests that confirm whether a certain image has changed significantly.

parameter type description

other mapnik.Image
another image instance

options [Object] (default {threshold:16,alpha:true})

parameter	type	description
other	`mapnik.Image`	another image instance
options	`[Object]` (default `{threshold:16,alpha:true}`)

Returns

number :

quantified visual difference between these two images

src/mapnik_image.cpp

`composite(other, callback)`

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

parameter type description

other mapnik.Image

callback Function

parameter	type	description
other	`mapnik.Image`
callback	`Function`

src/mapnik_image.cpp

`copy([options], callback)`

Copy this image data so that changes can be made to a clone of it.

parameter type description

options [Object] (default {})

callback Function

parameter	type	description
options	`[Object]` (default `{}`)
callback	`Function`

src/mapnik_image.cpp

`copySync([options])`

Copy this image data so that changes can be made to a clone of it.

parameter type description

options [Object] (default {})

parameter	type	description
options	`[Object]` (default `{}`)

Returns

mapnik.Image :

copy

src/mapnik_image.cpp

`demultiply(callback)`

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

parameter type description

callback Function

parameter	type	description
callback	`Function`

src/mapnik_image.cpp

`demultiplySync`

Demultiply the pixels in this image. The opposite of premultiplying

src/mapnik_image.cpp

`encode([format], callback)`

Encode this image into a buffer of encoded data

parameter type description

format [string] (default png)
image format

callback Function

parameter	type	description
format	`[string]` (default `png`)	image format
callback	`Function`

Returns

Buffer :

encoded image data

Examples

var fs = require('fs');
myImage.encode('png', function(err, encoded) {
  fs.writeFileSync('myimage.png', encoded);
});

src/mapnik_image.cpp

`encodeSync([format])`

Encode this image into a buffer of encoded data

parameter type description

format [string] (default png)
image format

parameter	type	description
format	`[string]` (default `png`)	image format

Returns

Buffer :

encoded image data

Examples

var fs = require('fs');
fs.writeFileSync('myimage.png', myImage.encodeSync('png'));

src/mapnik_image.cpp

`fill(color, callback)`

Asynchronously fill this image with a given color.

parameter type description

color mapnik.Color or number

callback Function

parameter	type	description
color	`mapnik.Color` or `number`
callback	`Function`

Examples

var im = new mapnik.Image(5, 5);
im.fill(1, function(err, im_res) {
  if (err) throw err;
  assert.equal(im_res.getPixel(0, 0), 1);
});

src/mapnik_image.cpp

`fillSync(color)`

Fill this image with a given color

parameter type description

color mapnik.Color or number

parameter	type	description
color	`mapnik.Color` or `number`

src/mapnik_image.cpp

`getPixel(x, y, options)`

parameter type description

x number
position within image from top left

y number
position within image from top left

options Object
the only valid option is get_color, which should be a boolean.

parameter	type	description
x	`number`	position within image from top left
y	`number`	position within image from top left
options	`Object`	the only valid option is `get_color`, which should be a `boolean`.

Returns

number :

color

Examples

var im = new mapnik.Image(256, 256);
var view = im.view(0, 0, 256, 256);
var pixel = view.getPixel(0, 0, {get_color:true});
assert.equal(pixel.r, 0);
assert.equal(pixel.g, 0);
assert.equal(pixel.b, 0);
assert.equal(pixel.a, 0);

src/mapnik_image.cpp

`height`

Get this image's height

Returns

number :

height

src/mapnik_image.cpp

`isSolidSync`

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

Returns

boolean :

whether the image is solid

Examples

var im = new mapnik.Image(256, 256);
var view = im.view(0, 0, 256, 256);
assert.equal(view.isSolidSync(), true);

src/mapnik_image.cpp

`premultiplied`

Determine whether the given image is premultiplied.

Returns

boolean :

premultiplied true if the image is premultiplied

src/mapnik_image.cpp

`premultiply(callback)`

Premultiply the pixels in this image, asynchronously

parameter type description

callback Function

parameter	type	description
callback	`Function`

src/mapnik_image.cpp

`premultiplySync`

Premultiply the pixels in this image

src/mapnik_image.cpp

`save(filename, [format])`

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

parameter type description

filename string

format [string] (default png)

parameter	type	description
filename	`string`
format	`[string]` (default `png`)

Examples

myImage.save('foo.png');

src/mapnik_image.cpp

`setPixel(x, y, numeric)`

parameter type description

x number
position within image from top left

y number
position within image from top left

numeric Object or number
or object representation of a color

parameter	type	description
x	`number`	position within image from top left
y	`number`	position within image from top left
numeric	`Object` or `number`	or object representation of a color

src/mapnik_image.cpp

`view(x, y, width, height)`

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

parameter type description

x number

y number

width number

height number

parameter	type	description
x	`number`
y	`number`
width	`number`
height	`number`

Returns

mapnik.Image :

an image constrained to this new view

src/mapnik_image.cpp

`width`

Get this image's width

Returns

number :

width

src/mapnik_image_view.cpp

`mapnik.ImageView(left, top, width, height)`

This is usually not initialized directly: you'll use the mapnik.Image#view method to instantiate an instance.

parameter type description

left number

top number

width number

height number

parameter	type	description
left	`number`
top	`number`
width	`number`
height	`number`

Throws

exception	description
`TypeError`	if any argument is missing or not numeric

Examples

var im = new mapnik.Image(256, 256);
var view = im.view(0, 0, 256, 256);

src/mapnik_map.cpp

`mapnik.Map(width, width, projection)`

A map in mapnik is an object that combined data sources and styles in a way that lets you produce styled cartographic output.

parameter type description

width number

width number

projection string
as a proj4 code

parameter	type	description
width	`number`
width	`number`
projection	`string`	as a proj4 code

Examples

var map = new mapnik.Map(25, 25, '+init=epsg:3857');

src/mapnik_map.cpp

`add_layer(new)`

Add a new layer to this map

parameter type description

new mapnik.Layer
layer

parameter	type	description
new	`mapnik.Layer`	layer

src/mapnik_map.cpp

`clear`

Remove all layers and styles from this map

src/mapnik_map.cpp

`clone`

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

Returns

mapnik.Map :

clone

src/mapnik_map.cpp

`font`

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

Returns

Array<string> :

fonts

src/mapnik_map.cpp

`fontDirectory`

Get the currently-registered font directory, if any

Returns

string or :

fonts

src/mapnik_map.cpp

`fontFiles`

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

Returns

Object :

fonts

src/mapnik_map.cpp

`fromStringSync(stylesheet, [options])`

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

parameter type description

stylesheet string
contents

options [Object] (default {})

parameter	type	description
stylesheet	`string`	contents
options	`[Object]` (default `{}`)

Examples

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

src/mapnik_map.cpp

`fromStringSync(stylesheet, [options], callback)`

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

parameter type description

stylesheet string
contents

options [Object] (default {})

callback Function

parameter	type	description
stylesheet	`string`	contents
options	`[Object]` (default `{}`)
callback	`Function`

Examples

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

src/mapnik_map.cpp

`get_layer(layer)`

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

parameter type description

layer string or number
name or index

parameter	type	description
layer	`string` or `number`	name or index

Returns

mapnik.Layer :

the layer

Throws

exception	description
`Error`	if index is incorrect or layer is not found

src/mapnik_map.cpp

`layers`

Get all of the currently-added layers in this map

Returns

Array<mapnik.Layer> :

layers

src/mapnik_map.cpp

`load(stylesheet, [options], callback)`

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

parameter type description

stylesheet string
path

options [Object] (default {})

callback Function

parameter	type	description
stylesheet	`string`	path
options	`[Object]` (default `{}`)
callback	`Function`

src/mapnik_map.cpp

`loadSync(stylesheet, [options])`

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

parameter type description

stylesheet string
path

options [Object] (default {})

parameter	type	description
stylesheet	`string`	path
options	`[Object]` (default `{}`)

Examples

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

src/mapnik_map.cpp

`resize(width, height)`

Give this map new dimensions

parameter type description

width number

height number

parameter	type	description
width	`number`
height	`number`

src/mapnik_map.cpp

`scale`

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

Returns

number :

scale

src/mapnik_map.cpp

`scaleDenominator`

Get the map's scale denominator.

Returns

number :

scale denominator

src/mapnik_projection.cpp

`mapnik.Projection(projection, [options])`

A geographical projection: this class makes it possible to translate between locations in different projections

parameter type description

projection string
projection as a proj4 definition string

options [Object] (default {lazy:false})
whether to lazily instantiate the data backing this projection.

parameter	type	description
projection	`string`	projection as a proj4 definition string
options	`[Object]` (default `{lazy:false}`)	whether to lazily instantiate the data backing this projection.

Throws

exception	description
`TypeError`	if the projection string or options argument is the wrong type
`Error`	the projection could not be initialized - it was not found in proj4's tables or the string was malformed

Examples

var wgs84 = new mapnik.Projection('+init=epsg:4326');

src/mapnik_projection.cpp

`forward(position)`

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

parameter type description

position Array<number>
as [x, y] or extent as [minx,miny,maxx,maxy]

parameter	type	description
position	Array<`number`>	as [x, y] or extent as [minx,miny,maxx,maxy]

Returns

Array<number> :

projected coordinates

Examples

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

src/mapnik_projection.cpp

`inverse(position)`

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

parameter type description

position Array<number>
as [x, y] or extent as [minx,miny,maxx,maxy]

parameter	type	description
position	Array<`number`>	as [x, y] or extent as [minx,miny,maxx,maxy]

Returns

Array<number> :

unprojected coordinates

src/mapnik_vector_tile.cpp

`mapnik.VectorTile(z, x, y)`

A generator for the Mapbox Vector Tile specification of compressed and simplified tiled vector data

parameter type description

z number

x number

y number

parameter	type	description
z	`number`
x	`number`
y	`number`

Examples

var vtile = new mapnik.VectorTile(9,112,195);

src/mapnik_vector_tile.cpp

`addData(raw, name)`

Add raw data to this tile as a Buffer

parameter type description

raw Buffer
data

name string
of the layer to be added

parameter	type	description
raw	`Buffer`	data
name	`string`	of the layer to be added

src/mapnik_vector_tile.cpp

`addGeoJSON(geojson, name)`

Add features to this tile from a GeoJSON string

parameter type description

geojson string
as a string

name string
of the layer to be added

parameter	type	description
geojson	`string`	as a string
name	`string`	of the layer to be added

src/mapnik_vector_tile.cpp

`clear(callback)`

Remove all data from this vector tile

parameter type description

callback Function

src/mapnik_vector_tile.cpp

`compositeSync(vector)`

Composite an array of vector tiles into one vector tile

parameter type description

vector Array<mapnik.VectorTile>
tiles

src/mapnik_vector_tile.cpp

`empty(whether)`

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

parameter type description

whether boolean
the layer is empty

src/mapnik_vector_tile.cpp

`getData(map, renderable, callback)`

Render this vector tile to a surface, like a mapnik.Image

parameter type description

map mapnik.Map
object

renderable mapnik.Image
surface

callback Function

src/mapnik_vector_tile.cpp

`getData`

Get the data in this vector tile as a buffer

Returns

Buffer :

raw data

src/mapnik_vector_tile.cpp

`height(height)`

Get the vector tile's height

parameter type description

height number

src/mapnik_vector_tile.cpp

`isSolid(callback)`

Test whether this tile is solid - whether it has features

parameter type description

callback Function

src/mapnik_vector_tile.cpp

`isSolidSync`

Test whether this tile is solid - whether it has features

Returns

boolean :

whether the tile is solid

src/mapnik_vector_tile.cpp

`names(layer)`

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

parameter type description

layer Array<string>
names

src/mapnik_vector_tile.cpp

`painted(painted)`

Get whether the vector tile has been painted

parameter type description

painted boolean

src/mapnik_vector_tile.cpp

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

Query a vector tile by longitude and latitude

parameter type description

longitude number

latitude number

options [Object] (default {tolerance:0})
tolerance: allow results that are not exactly on this longitude, latitude position.

callback Function

src/mapnik_vector_tile.cpp

`setData(raw, name)`

Replace the data in this vector tile with new raw data

parameter type description

raw Buffer
data

name string
of the layer to be added

src/mapnik_vector_tile.cpp

`toGeoJSON(callback)`

Get a GeoJSON representation of this tile

parameter type description

callback Function

Returns

string :

stringified GeoJSON of all the features in this tile.

src/mapnik_vector_tile.cpp

`toGeoJSONSync`

Get a GeoJSON representation of this tile

Returns

string :

stringified GeoJSON of all the features in this tile.

src/mapnik_vector_tile.cpp

`toJSON`

Get a JSON representation of this tile

Returns

Object :

json representation of this tile with name, extent, and version properties

src/mapnik_vector_tile.cpp

`width(width)`

Get the vector tile's width

parameter type description

width number

src/blend.cpp

`mapnik.blend(buffers, options, callback)`

Composite multiple images on top of each other, with strong control over how the images are combined, resampled, and blended.

parameter type description

buffers Array<Buffer>
an array of buffers

options Object
can include width, height, compression, reencode, palette, mode can be either hextree or octree, quality. JPEG & WebP quality quality ranges from 0-100, PNG quality from 2-256. Compression varies by platform - it references the internal zlib compression algorithm.

callback Function
called with (err, res), where a successful result is a processed image as a Buffer

Examples

mapnik.blend([
 fs.readFileSync('foo.png'),
 fs.readFileSync('bar.png'),
], function(err, result) {
 if (err) throw err;
 fs.writeFileSync('result.png', result);
});

parameter	type	description
map	`mapnik.Map`	object
renderable	`mapnik.Image`	surface
callback	`Function`

parameter	type	description
longitude	`number`
latitude	`number`
options	`[Object]` (default `{tolerance:0}`)	tolerance: allow results that are not exactly on this longitude, latitude position.
callback	`Function`

parameter	type	description
buffers	Array<`Buffer`>	an array of buffers
options	`Object`	can include width, height, `compression`, `reencode`, palette, mode can be either `hextree` or `octree`, quality. JPEG & WebP quality quality ranges from 0-100, PNG quality from 2-256. Compression varies by platform - it references the internal zlib compression algorithm.
callback	`Function`	called with (err, res), where a successful result is a processed image as a Buffer