Magnacarto

Recent versions of libproj no longer support the old +init=epsg:XXXX projection string style. By default, the mapnik3 builder emits the modern epsg:XXXX format.

If you need to maintain compatibility with older libproj or proj4 versions, use the mapnik3-proj4 builder.

Requirement: You must update the SRS (Spatial Reference System) of your layers in your .mml files to the new epsg:XXXX style. The mapnik3-proj4 builder will then automatically prepend the +init= prefix for you.

To create a MapServer file that only contains LAYERS and SYMBOLS (omitting the top-level MAP block), use the -ms-no-map-block option. This is ideal for creating snippets that you intend to INCLUDE into existing MapServer map files that already have custom metadata or image format configurations.

magnacarto -mml world.mml -builder mapserver -ms-no-map-block > layers.map

Use the magnacarto CLI to convert a Mapnik Markup Language (.mml) file into a Mapnik XML file. This XML file can then be used by rendering engines like nik2img.py.

magnacarto -mml world.mml > world.xml

Magnacarto supports several advanced features that extend the original CartoCSS specification.

Text placement list

You can replicate the Mapnik TextSymbolizer <Placement> list behavior using text-placement-list. This allows multiple styling definitions for a single label:

#labels {
    text-name: "[name]";
    text-face-name: "DejaVu Sans Book";
    text-size: 16;
    text-placement: point;
    text-dy: 8;
    text-fill: blue;
    text-placement-list:
        {text-size: 10; text-dy: -8; text-fill: red;},
        {text-fill: green; text-name: "[abbreviated_name]";},
        {text-fill: orange; text-dy: 8; text-name: "[nr]";};
}

Text Language

To set the <TextSymbolizer lang="[lang]"> attribute, use the text-lang property:

#labels {
    text-lang: "en";
}

To install Magnacarto, you need Go > 1.12 installed on your system.

1. Clone or download the repository.
2. Run make install to compile and install the binaries.

Render Plugins

Magnacarto supports rendering via Mapnik and MapServer through plugins:

• Mapserver: Included in the default magnaserv installation. Requires the mapserv binary to be in your PATH at runtime.
• Mapnik: Requires a separate compilation of the magnacarto-mapnik binary. You must have Mapnik (supporting version 3) installed with all header files, and mapnik-config must be in your PATH. Run make install to build this plugin binary.

Use the magnacarto CLI with the -builder mapserver flag to convert a .mml file into a MapServer .map file. This is useful for rendering maps with tools like shp2img.

magnacarto -mml world.mml -builder mapserver > world.map

go-mapnik is a Go wrapper for the Mapnik 3/4 API.

Prerequisites

You must have Mapnik installed on your system (libmapnik on Ubuntu/Debian, or mapnik via Homebrew on macOS).

Build Configuration

Since version 3, you must generate the system-dependent build flags manually. Run the following command in the package directory:

go generate .

This creates a build_config.go file containing the necessary flags.

Note on Dependency Management: Because go generate must be run to create build_config.go, this package does not work correctly via standard go get or direct imports. It is highly recommended to manually vendorize the package into your repository (e.g., using git subtree).

The magnaserv component includes logic to monitor MapML (.mml) and Mapnik Stylesheet (.mss) files for changes. When a file is modified, the service can automatically trigger a rebuild of the map style to provide real-time updates during development.

Key Behaviors

• Automatic MSS Discovery: If no specific .mss files are provided, the service parses the .mml file to identify and watch all stylesheets referenced within it.
• Editor Compatibility: The watcher includes a small delay (100ms) when detecting Rename operations to accommodate editors (like Vim) that perform atomic saves by renaming files, preventing

The magnacarto command-line tool converts CartoCSS (.mss) files into Mapnik (.mml) or MapServer styles. It supports multiple builder types, including Mapnik 3, Mapnik 3 with Proj4 support, and MapServer.

Basic Usage

To convert a single MSS file to a Mapnik style, provide the -mml flag (for the output MML file) and the -mss flag for the input CartoCSS file.

# Convert a single MSS file to Mapnik 3 style
magnacarto -mml output.mml -mss input.mss

# Convert multiple MSS files
magnacarto -mml output.mml -mss file1.mss -mss file2.mss

# Output to stdout
magnacarto -mml - -mss input.mss

You can use the mapnik package to load map configurations and render them to files, []byte, or image.Image.

Key capabilities include:

• Setting the scale denominator or scale factor.
• Enabling or disabling specific layers.
• Resizing the output dimensions.
• Using ZoomTo to define the geographic extent.

To render a map, create a new instance with mapnik.New(), load an XML configuration file, and call RenderToFile with a mapnik.RenderOpts object.

func Example() {
	m := mapnik.New()
	if err := m.Load("test/map.xml"); err != nil {
		log.Fatal(err)
	}
	m.Resize(1000, 500)
	m.ZoomTo(-180, -90, 180, 90)
	opts := mapnik.RenderOpts{Format: "png32"}
	if err := m.RenderToFile(opts, "/tmp/go-mapnik-example-1.png"); err != nil {
		log.Fatal(err)
	}
}

The following flags are used when generating MapServer files via the magnacarto CLI:

• -mml <file>: The input Mapnik Markup Language file.
• -builder mapserver: Specifies that the output should be formatted for MapServer.
• -ms-no-map-block: Prevents the creation of the MAP block, outputting only LAYERS and SYMBOLS.