emscripten-opencv

Or how to use opencv as a dependency in WebAssembly (wasm) code. This repository is an attempt at doing very basic image tasks like:

• Decoding an image into a Mat.
• Doing some matrix processing.
• Exposing matrix data back to JavaScript.

Setup

You need to have emscripten installed and accessible (source the shell scripts). You also need OpenCV source code to be able to compile its wasm version. Adapt the CMakeLists.txt to the location of your OpenCV directory.

Activate Emscripten in the shell

You can add some code to your shell config file. Personally I just run the following (fish shell) when I need it.

source ~/programs/emsdk/emsdk_env.fish

Build OpenCV.js

OpenCV.js is the name of the Emscripten build of OpenCV. In our case, we are building it for WebAssembly (wasm).

python ./platforms/js/build_js.py build_wasm --build_wasm

PS: You can modify the build_js.py file to enable/disable modules.

Building this example with Emscripten

mkdir build
cd build
emconfigure cmake ..
emmake make

Running the example in the browser

After building the example, just deploy a static http server at the root of this repository.

python -m http.server 8080

Then open your localhost page, and look at the dev tools console.