# PyMGL: Maplibre GL Native Static Renderer for Python

This package provides an interface to `mapblibre-gl-native` to render Mapbox GL
styles to PNG images.

WARNING: this package is under active development and the API may change without notice.

## Goals

This package is intended to provide a lightweight interface to `maplibre-gl-native`
for rendering Mapbox GL to PNG image data using Python. This is particularly useful for
server-side rendering of maps for use in reports.

This package provides only the Python API for interacting with `maplibre-gl-native`;
it does not provide higher-level functionality such as a web server or a CLI.

For a stand-alone service implmenting rendering functionality, see
[mbgl-renderer](https://github.com/consbio/mbgl-renderer) (implemented in NodeJS).

## Install

### Supported operating systems

#### MacOS 10.15+ (x86_64 only)

Wheels are available on PyPI:

```bash
pip install pymgl
```

To verify that it installed correctly, run the included test suite:

```bash
python -m pip install pytest Pillow numpy pixelmatch python-dotenv
python -m pytest --pyargs pymgl -v
```

#### Ubuntu 22.04 & 20.04

Due to the complexity of building manylinux wheels that include OpenGL and
successfully compile `maplibre-gl-native`, wheels are only available for
Ubuntu 22.04 and 20.04.

Wheels are available on the release page in Github. Download and install from there.

Unfortunately, Python wheel names are very restrictive, so we have added
`.ubuntu-22.04` and `.ubuntu-20.04` suffixes to the wheel names, which have to
be stripped off before you can install them.

Something like this for Ubuntu 22.04:

```bash

wget https://github.com/brendan-ward/pymgl/releases/download/<release>/pymgl-<release>-<Python version>-<Python version>-linux_x86_64.whl.ubuntu-22.04
# rename file to remove .ubuntu-22.04 suffix
find . -type f -name  "*.whl.ubuntu-22.04" -print0 -exec bash -c 'mv "${0}" "${0//.ubuntu-22.04/}"' {} \;
python3 -m pip install --find-links . pymgl
```

You also need to install the following runtime dependencies:

**Ubuntu 22.04:**

```bash
apt-get install
    libicu70 \
    libcurl4 \
    libjpeg-turbo8 \
    libpng16-16 \
    libprotobuf23 \
    libuv1 \
    libx11-6 \
    libegl1 \
    libopengl0 \
    xvfb
```

**Ubuntu 20.04:**

```bash
apt-get install
    libicu66 \
    libcurl4 \
    libjpeg-turbo8 \
    libpng16-16 \
    libprotobuf17 \
    libuv1 \
    libx11-6 \
    libegl1 \
    libopengl0 \
    xvfb
```

You must have Xvfb running in order to successfully use `pymgl`. You can
setup and run Xvfb manually, or wrap calls to python in `Xvfb-run`.

To verify that it installed correctly, run the included test suite:

```bash
python -m pip install pytest Pillow numpy pixelmatch python-dotenv
xvfb-run -a --server-args="-screen 0 1024x768x24 -ac +render -noreset" \
    python -m pytest --pyargs pymgl -v
```

#### Windows

Windows is not and will not be supported.

## Usage

To create a map object, you must always provide a Mapbox GL style JSON string or
URL to a well-known style hosted by Mapbox or Maptiler:

```Python
from pymgl import Map

style = """{
    "version": 8,
    "sources": {
        "basemap": {
            "type": "raster",
            "tiles": ["https://services.arcgisonline.com/arcgis/rest/services/Ocean/World_Ocean_Base/MapServer/tile/{z}/{y}/{x}"],
            "tileSize": 256
        }
    },
    "layers": [
        { "id": "basemap", "source": "basemap", "type": "raster" }
    ]
}"""

map = Map(style, <height=256>, <width=256>, <ratio=1>, <longitude=0>, <latitude=0>, <zoom=0>, <token=None>, <provider=None>)
```

See the [styles](#styles) section for more information about map styles.

Other than style, all other parameters are optional with default values.

NOTE: `style` and `ratio` cannot be changed once the instance is constructed.

You can use a well-known style instead of providing a style JSON string, but
you must also provide a token and identify the correct provider:

```Python
map = Map("mapbox://styles/mapbox/streets-v11", token=<mapbox token>, provider="mapbox")
```

Valid providers are `mapbox`, `maptiler`, and `maplibre`.

### Map properties

You can set additional properties on the map instance after it is created:

```Python
map.setCenter(longitude, latitude)

map.setZoom(zoom)

map.setSize(width, height)

map.setBearing(bearing)  # map bearing in degrees

map.setPitch(pitch)  # map pitch in degrees

map.setFilter(layerId, filterJSON or None)

map.setPaintProperty(layerId, property, value)

map.setVisibility(layerId, True / False)
```

You can retrieve these values using attributes, if needed:

```Python
map.size  # (width, height)

map.center  # (longitude, latitude)

map.zoom

map.bearing

map.pitch
```

You can also retrive information about the map's style or a specific layer:

```Python
map.listLayers()  # [<layerId1>, ...]

map.listSources()  # [<sourceId1>, ...]

map.getFilter(<layerId>)  # returns JSON value or None

map.getPaintProperty(<layerId>, <property>)  # returns JSON value or None

map.getLayerJSON(<layerId>)  # returns JSON describing layer
```

NOTE: paint properties may be decoded to their internal representation. For
example, a CSS color string `#FF0000` will be returned as `["rgba", 255, 0, 0, 1]`.

IMPORTANT: if you are using a remotely-hosted style, you need to force the map
to load - which loads all underying assets - before listing the style's layers,
sources, or other properties.

```Python
map = Map("mapbox://styles/mapbox/streets-v11", token=<mapbox token>, provider="mapbox")

map.listLayers()  # []
map.load()
map.listLayers()  # [<layerId1>, ...]
```

Alternatively, you can download the style yourself and provide that as input to
the Map, and it will show all layers without requiring a render first. However, not all assets will be loaded until the first render.

```Python
from urllib.request import urlopen

url = f"https://api.mapbox.com/styles/v1/mapbox/streets-v11?access_token={MAPBOX_TOKEN}"

with urlopen(url) as r:
    style = r.read()

map = Map(style.decode("UTF-8") token=<mapbox token>, provider="mapbox")
map.listLayers()  # [<layerId1>, ...]
```

You can auto-fit the map to bounds instead of using center longitude / lantitude
and zoom:

```Python
map.setBounds(xmin, ymin, xmax, ymax, <padding=0>)
```

You can register an image for use with your style by providing an ID,
raw image bytes, width, height, pixel ratio, and indicate if it should be
interpreted as SDF:

```
map.addImage("id", img_bytes, width, height, <ratio=1>, <make_SDF=False>)
```

See the [SDF image docs](https://docs.mapbox.com/help/troubleshooting/using-recolorable-images-in-mapbox-maps/) for more information about using SDF
images.

### Rendering

You can render the map to PNG bytes:

```Python
img_bytes = map.renderPNG()
```

This returns `bytes` containing the RGBA PNG data.

You can render the map to a raw buffer as a numpy array (`uint8` dtype):

```Python
array = map.renderBuffer()
```

The array is a sequence of RGBA values for each pixel in the image.

This may be useful if you are going to immediately read the image data into
another package such as `Pillow` or `pyvips` to combine with other image
operations.

### Map instances

WARNING: you must manually delete the map instance if you assign a new map
instance to that variable, or this package will segfault (not yet sure why).
This problem does not occur if separate instances are assigned to separate
variables.

```Python

map = Map(<style>, <width>, <height>)

del map  # must manually delete BEFORE creating a new instance assigned to this

map = Map(<style>, <width>, <height>)
```

For this reason, you should consider using a context manager:

```Python
with Map(<style>, <width>, <height>) as map:
    map.renderPNG()
```

You can also use the map instance to directly render to PNG, if you don't need
to set other properties on the map instance:

```
Map(<style>, <width>, <height>).renderPNG()
```

## Styles

PyMGL should support basic styles as of Mapbox GL JS 1.13.

### Remote tilesets, sources, and assets

Remote tilesets, tile sources, and assets (glyphs, sprites) should be well-supported.
These are loaded by the underlying C++ library outside our control. Invalid
URLs will generally raise errors. However, network timeouts or incorrect formats
may cause the process to crash.

### Local mbtiles

Local MBTiles are supported, but must be provided using an absolute path to the
mbtiles file as the source `url` of a tileset; it must resolve to an actual file.

Local MBTiles are denoted with a `mbtiles://` URI prefix.

Example:

```json
{
    "sources": {
        "source_id": {
            "url": "mbtiles:///<pymgl_root_dir>/tests/fixtures/geography-class-png.mbtiles",
            ...
        }
    },
    "layers": [...],
    ...
}
```

### Local files

GeoJSON files and other local file assets are supported, but must be provided
using an absolute path to the file source.

Example:

```json
{
    "sources": {
        "geojson": {
            "type": "geojson",
            "data": "file:///<pymgl_root_dir>/tests/fixtures/test.geojson"
        }
    },
    "layers": [...],
    ...
}

```

WARNING: providing a URI to tiles under the `tiles` key of a source is NOT currently supported by Maplibre GL Native;
attempting to do so will fail.

### Images

You must register the image with the map instance before rendering the map. See
`map.addImage()` above.

```json
{
    "sources": {...},
    "layers": [
        {
            ...,
            "paint": {
                "fill-pattern": "pattern"
            }
        },
    ]
}
```

You can use map images as fill patterns or icon images.

### Adding sources and layers after construction

You can add sources and layers dynamically after constructing the map instance:

```Python
import json

map = Map("")  # construct with empty style

map.addSource("my_id", json.dumps({
    "type": "geojson",
    "data": {"type": "Point", "coordinates": [0, 0]}
}))

map.addLayer(json.dumps({
    "id": "geojson-point",
    "source": "geojson",
    "type": "circle",
    "paint": { ... }
}))
```

### Feature state

You can get, set, and remove feature state after the map has been loaded.

```Python

map = Map(<style with source "exampleSource" and layer "exampleLayer">, ...)

map.load()
map.getFeatureState("exampleSource", "exampleLayer", "0")  # returns None
map.setFeatureState("exampleSource", "exampleLayer", "0", "{\"a\": true}")
map.getFeatureState("exampleSource", "exampleLayer", "0")  # returns "{\"a\": true}"

# remove the state value for key "a"
map.removeFeatureState("exampleSource", "exampleLayer", "0", "a")
map.render()
map.getFeatureState("exampleSource", "exampleLayer", "0")  # returns None
```

NOTE: features must already have a unique, numeric ID set on each feature. There
is currently no support for `promoteId` like in MapLibre GL JS.

IMPORTANT: the map must be loaded before getting or setting feature state. You
must manually force a render in order for the map to update feature state after
removing a state key

### Unsupported features

PyMGL does not support alternative projections or 3D terrain.

## Developing

### Dependencies:

#### MacOS:

Developing on MacOS requires the following binary libraries to be installed
via `homebrew`:

-   cmake
-   ninja

#### Developing on Ubuntu 22.04 or 20.04 requires the following binary libraries:

-   cmake
-   ninja-build
-   build-essential
-   libcurl4-openssl-dev
-   libicu-dev
-   libpng-dev
-   libprotobuf-dev
-   libturbojpeg0-dev
-   libx11-dev
-   libegl-dev
-   libopengl-dev
-   xvfb

To run on Linux, XVFB must also be running; otherwise the process will segfault.

See [`docker/README.md`](./docker/README.md) for more information.

#### Developing on other Linux versions

See `.github/workflows/build_wheels.yml` for the overall structure for building
and testing on Linux. You will most likely need to adapt the names of the
packages to the package manager for your version of Linux.

##### Debian Bullseye

We've heard (#7) that it is possible to successfully build and operate PyMGL
on Debian Bullseye with the following dependencies:

Build:

```bash
apt-get -y install \
    curl \
    build-essential \
    cmake \
    ccache \
    ninja-build \
    pkg-config \
    libcurl4-openssl-dev \
    libicu-dev \
    libturbojpeg0-dev \
    libpng-dev \
    libprotobuf-dev \
    libuv1-dev \
    libx11-dev \
    libegl-dev \
    libopengl-dev \
    xvfb \
    libjpeg-dev \
    libsqlite3-dev \
    libopengl0 \
    git
```

Runtime:

```bash
apt install --no-install-recommends -y \
    xvfb \
    xauth \
    curl \
    libicu67 \
    libjpeg-turbo-progs \
    libpng16-16 \
    libprotobuf23 \
    libuv1 \
    libx11-6 \
    libegl1 \
    libopengl0
```

### nanobind

`nanonbind` is used to provide bindings for Python against a C++ class that wraps
`maplibre-gl-native` for easier rendering operations.

It is included here as a git submodule, per the
[installation instructions]().

```bash
git submodule add https://github.com/wjakob/nanobind vendor/nanobind
cd vendor/nanobind
git submodule update --init --recursive
```

### Maplibre-gl-native

Maplibre-gl-native is included as a git submodule, and it includes many submodules
of its own.

```bash
git submodule add -b master https://github.com/maplibre/maplibre-gl-native vendor/maplibre-gl-native
```

### Git submodules

Run

```bash
git submodule update --init
```

We only need some of the submodules under maplibre-gl-native. In particular,
we do not need `maplibre-gl-js` or Android / IOS dependencies.

Run the following:

```bash
cd vendor/maplibre-gl-native

git submodule update --init --recursive \
    vendor/boost \
    vendor/cpp-httplib \
    vendor/earcut.hpp \
    vendor/eternal \
    vendor/googletest \
    vendor/polylabel \
    vendor/protozero \
    vendor/mapbox-base \
    vendor/unique_resource \
    vendor/vector-tile \
    vendor/wagyu \
    vendor/zip-archive
```

To later update `maplibre-gl-native`:

```bash
cd vendor/maplibre-gl-native
git checkout main
git pull origin

cd ../..
git commit -am "update maplibre-gl-native" to latest
```

### Architecture

This package is composed of 2 main parts:

-   wrapper around Maplibre GL native classes to make constructing and managing
    properties of the map easier
-   Python bindings created using nanobind against that wrapper

The wrapper is located in `src/map.cpp`.

### Build

#### C++ tests

See [tests/README](tests/README.md) for more information.

Building using CMake directly is useful when building the C++ level tests of the
Maplibre GL wrapper.

```bash
mkdir build

cd build

cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Debug

ctest -V
```

#### Build Python extension

The Python `setup.py` script manages building the library and extension using
CMake.

From project root directory:

```bash

python setup.py build_ext --inplace
```

#### Docstrings / type information

Docstrings are maintained in both `src/_pymgl.cpp` and `pymgl/__init__.pyi`.

Python-friendly type annotations are maintained in `pymgl/__init__.pyi`.

Note: `pymgl/__init__.pyi` is necessary to support autocompletion and tooltips
in VSCode.

## See also

[mbgl-renderer](https://github.com/consbio/mbgl-renderer)
provides a NodeJS API, CLI, and server based on the NodeJS bindings to Mapbox GL Native.

## Credits

This project was developed with the support of the
[U.S. Fish and Wildlife Service](https://www.fws.gov/)
[Southeast Conservation Adaptation Strategy](https://secassoutheast.org/) for
use in the
[Southeast Conservation Blueprint Viewer](https://blueprint.geoplatform.gov/southeast/)
and
[South Atlantic Conservation Blueprint Simple Viewer](https://blueprint.geoplatform.gov/southatlantic/).

This project is made possible because of the
[mapbox-gl-native](https://github.com/mapbox/mapbox-gl-native/) project by
[Mapbox](https://www.mapbox.com/)
by the efforts of the Maplibre community maintaining the open-source fork of that
project at [maplibre-gl-native](https://github.com/mapbox/mapbox-gl-native/).