wasm-marching-squares

This library is a direct port of rveciana's raster-marching-squares to WebAssembly by way of C. The algorithm is implemented in C and currently generates GeoJSON isolines given raw data from a GeoTIFF file. Isobands will be supported in the future.

Usage

WIP

For now, you can check out the test folder and see how the map.js file is using the WASM module. In the future, the external API will be much easier to use.

Caveats

• Need to add a cleaner external API for ease of use.
• Isoband generation is not implemented yet

Build

To properly build, you will need to download the Emscripten SDK.

1. Compile the Jansson C JSON library using emcc

   • Remove CMakeCache.txt from `include/jansson-2.13.1 if it exists
   • cd include/jansson-2.13.1 && emcmake cmake -DCMAKE_INSTALL_PREFIX:PATH=./emcc-lib .
   • emmake make VERBOSE=1
   • emmake make check
   • emmake make install

2. Generate the WASM code and JavaScript 'glue' code

./build

Test

C Library Unit Testing

1. Compile the Jansson C JSON library using cmake

   • Remove CMakeCache.txt from `include/jansson-2.13.1 if it exists
   • cd include/jansson-2.13.1 && cmake .
   • emmake make VERBOSE=1
   • emmake make check
   • emmake make install

2. Compile and run the unit tests

cd test && ./test

Functional Testing

• Start a webserver and serve the test directory
• Navigate to the index.html and click Test GeoJSON
• You can test the vardah.tif file or the sfctmp.tif file by altering the test/map.js file.

TODO

• Implement Isoband generation
• Speed up lookups using a Quadtree