https://github.com/springmeyer/utfgrid-example-writers
Simple reference implementations for creating UTGGrid tiles
https://github.com/springmeyer/utfgrid-example-writers
Last synced: 12 months ago
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Simple reference implementations for creating UTGGrid tiles
- Host: GitHub
- URL: https://github.com/springmeyer/utfgrid-example-writers
- Owner: springmeyer
- Created: 2012-02-07T19:06:45.000Z (over 14 years ago)
- Default Branch: master
- Last Pushed: 2012-02-12T18:37:28.000Z (over 14 years ago)
- Last Synced: 2025-04-19T21:25:36.309Z (about 1 year ago)
- Language: Python
- Homepage:
- Size: 333 KB
- Stars: 17
- Watchers: 3
- Forks: 6
- Open Issues: 1
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Metadata Files:
- Readme: README.md
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README
# UTFGrid Example Writers
Sample implementations for writing UTFGrids.
For details on the UTFGrid spec see:
https://github.com/mapbox/utfgrid-spec
## Background
These examples are designed to be simple and with few dependencies.
They demonstrate how to author UTFGrids, but not how to serve them. For server implementations see:
https://github.com/mapbox/utfgrid-spec/wiki/Implementations
Currently the only production-ready write implementation for UTFGrids is found inside Mapnik's
[grid_renderer](https://github.com/mapnik/mapnik/tree/master/include/mapnik/grid) which
which uses AGG rendering to quickly render a feature hit grid in a single pass over geometries.
Mapnik's [python](https://github.com/mapnik/mapnik/blob/master/bindings/python/python_grid_utils.hpp)
or [node.js](https://github.com/mapnik/node-mapnik/blob/master/src/js_grid_utils.hpp)
bindings can then be used to encode to UTFGrid format as JSON objects.
Because this Mapnik implementation is complex, and written in C++, simpler examples are needed
that prioritize simplicity and ease of understanding over rendering speed.
## Reference Implementations
1) ogr_renderer.py
This uses the [OGR library](http://www.gdal.org/ogr) and its python bindings to query
a polygon shapefile, build a pixel buffer of feature ids, and then encode those
ids in UTFGrid format.
View a sample grid in your terminal by doing:
python ogr_renderer.py
And pretty print the json like:
python ogr_renderer.py | python -mjson.tool
2) mapnik_renderer.py
This sample matches the ogr example, but uses Mapnik's AGG-based scanline rendering of grid ids, which is sensitive to the exact styles applied to geometries - allowing it to work equally well for encoding interactive pixels of both points, lines, polygons, text, and svg/png symbols (their shape).
This example requires Mapnik >= 2.0.0.
View the sample output like:
python mapnik_renderer.py | python -mjson.tool
3) fiona_rtree_renderer.py
This one uses an in memory rtree index to speed up the loop creating the grid, and a fiona collection to read the shapefile.