/openexr-wrap-em

Emscripten wrapper of OpenEXR

Primary LanguageC++

EXR Wrapper

This wrapper is intended to be used via emscripten to interface with OpenEXR from JavaScript. It has the following dependencies:

  • emscripten: To compile the dependencies and the wrapper itself. Tested version is emscripten-1.38.12.
  • OpenEXR: The main library. Tested version is 2.2.1. Both the openexr and the ilmbase libraries are required.
  • zlib: Dependency for OpenEXR. Tested version is 1.2.11.

Compiling

In general, compiling with emscripten is quite annoying. The emconfigure and emmake tools can help building the dependencies. To run the compiled javascript applications, node, which is also part of emscripten, can be used. The result of the build process is a pair of files, exr-wrap.js and exr-wrap.wasm. LTO and other options can be set for more optimization, but their use is somewhat questionable.

  1. Prepare 0. mkdir install 0. export WRAPPER_INSTALL=$(pwd)/install
  2. Building zlib 0. cd $zlibdir
    1. emconfigure ./configure --prefix $WRAPPER_INSTALL
    2. Edit the Makefile: AR=emar, ARFLAGS=r, CFLAGS+=-O3
    3. Optionally add --llvm-lto 1 to CFLAGS
    4. emmake make -j12 && make install
  3. Building ilmbase 0. cd $ilmbasedir && mkdir build && cd build
    1. emconfigure cmake .. -DCMAKE_INSTALL_PREFIX=$WRAPPER_INSTALL -DCMAKE_BUILD_TYPE=Release
    2. Possibly remove incorrect quotes around the node path in CMakeLists.txt
    3. Edit config/IlmBaseConfig.h, setting HAVE_PTHREAD 0.
    4. Optionally add --llvm-lto 1 to compiler and linker flags and set -O3.
    5. emmake make -j12 && make install
  4. Building openexr 0. cd openexr && mkdir build && cd build
    1. emconfigure cmake .. -DCMAKE_INSTALL_PREFIX=$WRAPPER_INSTALL -DCMAKE_BUILD_TYPE=Release -DILMBASE_PACKAGE_PREFIX=$WRAPPER_INSTALL
    2. Possibly set ZLIB_LIBRARY and ZLIB_INCLUDE_DIR
    3. Optionally add --llvm-lto 1 to compiler and linker flags and set -O3.
    4. emmake make -j12 && make install
    5. Building the dwaLookups.h and b44ExpLogTable.h headers requires using node to run the javascript programs built for this purpose. Building with make VERBOSE=1 can help figuring out the exact parameters. Use node to run the created .js programs. Alternatively, copy the two headers from a native build.
  5. Building the wrapper 0. cd wrapp
    1. make