f88666eb47
after:
24d7f9cb Switch code to SDL2.
fixes:
webp_wasm.js:1 Uncaught TypeError: Cannot read properties of null
(reading 'addEventListener')
at Object.registerOrRemoveHandler (webp_wasm.js:1:101330)
at registerMouseEventCallback (webp_wasm.js:1:154227)
at _emscripten_set_mousemove_callback_on_thread (webp_wasm.js:1:155015)
...
The SDL2 port forces the canvas id to '#canvas':
324df6865a/src/video/emscripten/SDL_emscriptenvideo.c (L210)
This change maps '#output_canvas' to this entry in specialHTMLTargets[]:
https://emscripten.org/docs/api_reference/html5.h.html
https://github.com/libsdl-org/SDL/issues/5260 &
https://github.com/emscripten-ports/SDL2/issues/130 may also be related.
Change-Id: I26f4aa22b9d68b0fc45b83edfe6fe074b59a82a7
Test: emscripten 3.1.16
WebP JavaScript decoder
__ __ ____ ____ ____ __ ____
/ \\/ \ _ \ _ \ _ \ (__)/ __\
\ / __/ _ \ __/ _) \_ \
\__\__/_____/____/_/ /____/____/
This file describes the compilation of libwebp into a JavaScript decoder using Emscripten and CMake.
-
install the Emscripten SDK following the procedure described at: https://emscripten.org/docs/getting_started/downloads.html#installation-instructions-using-the-emsdk-recommended After installation, you should have some global variable positioned to the location of the SDK. In particular, $EMSDK should point to the top-level directory containing Emscripten tools.
-
configure the project 'WEBP_JS' with CMake using:
cd webp_js && \ emcmake cmake -DWEBP_BUILD_WEBP_JS=ON ../ -
compile webp.js using 'emmake make'.
-
that's it! Upon completion, you should have the 'webp.js', 'webp.js.mem', 'webp_wasm.js' and 'webp_wasm.wasm' files generated.
The callable JavaScript function is WebPToSDL(), which decodes a raw WebP bitstream into a canvas. See webp_js/index.html for a simple usage sample (see below for instructions).
Demo HTML page
The HTML page webp_js/index.html requires the built files 'webp.js' and 'webp.js.mem' to be copied to webp_js/. An HTTP server to serve the WebP image example is also needed. With Python, just run:
cd webp_js && python3 -m http.server 8080
and then navigate to http://localhost:8080 in your favorite browser.
Web-Assembly (WASM) version:
CMakeLists.txt is configured to build the WASM version when using the option WEBP_BUILD_WEBP_JS=ON. The compilation step will assemble the files 'webp_wasm.js' and 'webp_wasm.wasm' that you then need to copy to the webp_js/ directory.
See webp_js/index_wasm.html for a simple demo page using the WASM version of the library.
Caveats
- First decoding using the library is usually slower, due to just-in-time compilation.