Dear ImGui Bundle development doc

Developer notes / emscripten

Install emscripten: see https://emscripten.org/docs/getting_started/downloads.html or use external/hello_imgui/hello_imgui/tools/emscripten/install_emscripten.sh

Build imgui_bundle for emscripten

mkdir build_ems
cd build_ems
source ~/emsdk/emsdk_env.sh
emcmake cmake .. -DCMAKE_BUILD_TYPE=Release  # This will download a precompiled version of OpenCV4.7.0 for emscripten
make -j

Test:

python -m http.server

Then open http://localhost:8000/bin/ in a browser

How to build the precompiled OpenCV package for emscripten

Docs and tricks, cf:

Clone Opencv 4.7.0

git clone https://github.com/opencv/opencv.git
cd opencv
git checkout 4.9.0
cd ..

Build (with cmake command extracted from build_js.py)

source ~/emsdk/emsdk_env.sh
mkdir build
cd build

EMSDK=~/emsdk
OPENCV_SRC=$(pwd)/../opencv
OPENCV_INSTALL=$(pwd)/../opencv_emscripten_install
TOOLCHAIN=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
PYTHON_EXE=$(which python3)

Manually edit opencv/CMakeList.txt, and add:
    add_compile_options(-pthread)
    add_link_options(-pthread)


Note: to compile without pthread support,
    * remove -pthread below
    * replace *twice* "-s USE_PTHREADS=1" by "-s USE_PTHREADS=0"


emcmake cmake \
-S ../opencv -B . \
-DPYTHON_DEFAULT_EXECUTABLE=$PYTHON_EXE \
-DCMAKE_BUILD_TYPE=Release \
-DCMAKE_INSTALL_PREFIX=$OPENCV_INSTALL \
-DCMAKE_TOOLCHAIN_FILE=$TOOLCHAIN \
\
\"-DCMAKE_C_FLAGS='-pthread -s WASM=1 -s USE_PTHREADS=1 ' \"  \
\"-DCMAKE_CXX_FLAGS='-pthread -s WASM=1 -s USE_PTHREADS=1 ' \" \
\
-DCPU_BASELINE='' -DCPU_DISPATCH='' -DENABLE_PIC=FALSE -DCV_TRACE=OFF -DBUILD_SHARED_LIBS=OFF -DWITH_1394=OFF -DWITH_ADE=OFF -DWITH_VTK=OFF -DWITH_EIGEN=OFF -DWITH_FFMPEG=OFF -DWITH_GSTREAMER=OFF -DWITH_GTK=OFF -DWITH_GTK_2_X=OFF -DWITH_IPP=OFF -DWITH_JASPER=OFF -DWITH_JPEG=ON -DWITH_WEBP=OFF -DWITH_OPENEXR=OFF -DWITH_OPENGL=OFF -DWITH_OPENVX=OFF -DWITH_OPENNI=OFF -DWITH_OPENNI2=OFF -DWITH_PNG=ON -DWITH_TBB=OFF -DWITH_TIFF=OFF -DWITH_V4L=OFF -DWITH_OPENCL=OFF -DWITH_OPENCL_SVM=OFF -DWITH_OPENCLAMDFFT=OFF -DWITH_OPENCLAMDBLAS=OFF -DWITH_GPHOTO2=OFF -DWITH_LAPACK=OFF -DWITH_ITT=OFF -DWITH_QUIRC=ON -DBUILD_ZLIB=ON -DBUILD_opencv_apps=OFF -DBUILD_opencv_calib3d=ON -DBUILD_opencv_dnn=ON -DBUILD_opencv_features2d=ON -DBUILD_opencv_flann=ON -DBUILD_opencv_gapi=OFF -DBUILD_opencv_ml=OFF -DBUILD_opencv_photo=ON -DBUILD_opencv_imgcodecs=ON -DBUILD_opencv_shape=OFF -DBUILD_opencv_videoio=OFF -DBUILD_opencv_videostab=OFF -DBUILD_opencv_highgui=OFF -DBUILD_opencv_superres=OFF -DBUILD_opencv_stitching=OFF -DBUILD_opencv_java=OFF -DBUILD_opencv_js=OFF -DBUILD_opencv_python2=OFF -DBUILD_opencv_python3=OFF -DBUILD_EXAMPLES=ON -DBUILD_PACKAGE=OFF -DBUILD_TESTS=ON -DBUILD_PERF_TESTS=ON -DBUILD_DOCS=OFF -DWITH_PTHREADS_PF=OFF -DCV_ENABLE_INTRINSICS=OFF -DBUILD_WASM_INTRIN_TESTS=OFF \


make -j
make install

Deploy to github

tar cvfz opencv_4.9_pthread_emscripten_install.tgz opencv_emscripten_install

Then upload this to a release archive.