image-binarization-cpp-wasm

Image binarization using otsu's method on HTML ImageData in c++, compiled to WASM for the web.

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See In action: Web Demo

• note: Demo loads the .wasm file without the glue code.

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Build

• Requires Emscripten.

$ em++ img_processing.cpp -s ALLOW_MEMORY_GROWTH=1 -s STANDALONE_WASM -s EXPORTED_FUNCTIONS="['_otsuBinarize', '_malloc', '_free']" -Os -o img_processing.wasm

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Note: when loading wasm with WebAssembly.instantiateStreaming on a local test server

• The server must be configured to serve the .wasm file with the correct MIME type by sending the Content-Type: application/wasm header
• Example: configured python http.server script:

import http.server, socketserver

PORT = 8000
Handler = http.server.SimpleHTTPRequestHandler

Handler.extensions_map['.wasm'] = 'application/wasm'

with socketserver.TCPServer(("", PORT), Handler) as httpd:
    print("serving at port", PORT)
    httpd.serve_forever()

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References

• Otsu thresholding — image binarization by HBY coding academic
• otsu's method Wikipedia
• Loading WebAssembly modules efficiently