Web worker feature

[kalwalt]

• WASM in a single file
• deleting libjpeg refs. because included by emscripten with USE_LIBJPEG
• stb image for emscripten (linux?)

These changes to upgrade the project, and to test with WebWorker.

[kalwalt]

i can not compile the project it fails with this error, related to jpeg lib:

[100%] Linking CXX executable artoolkitx.js
cd /home/walter/kalwalt-github/artoolkitX_em_2d/Source/build-em/artoolkitx.js && /usr/bin/cmake -E cmake_link_script CMakeFiles/artoolkitx.dir/link.txt --verbose=1
/home/walter/emsdk/fastcomp/emscripten/em++   -s USE_LIBJPEG=1 -O3 -s ASSERTIONS=0 --llvm-lto 1 --memory-init-file 0 -s INVOKE_RUN=0 -s NO_EXIT_RUNTIME=1 -msse -msse2 -msse3 -mssse3 -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1 -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/core/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/highgui/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/imgcodecs/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/videoio/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/imgproc/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/calib3d/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/features2d/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/flann/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/depends/emscripten/opencv-3.4.1/modules/video/include -I/home/walter/kalwalt-github/artoolkitX_em_2d/Source/ARX/OCVT/include -DNDEBUG -O3  -O3  -s MODULARIZE_INSTANCE=1 -s USE_ES6_IMPORT_META=0 -s EXPORT_NAME='artoolkitXjs' -s EXPORT_ES6=1  -s BINARYEN_TRAP_MODE=clamp -s SINGLE_FILE=1   --pre-js /home/walter/kalwalt-github/artoolkitX_em_2d/Source/artoolkitx.js/ARX_wasmLoader.js -s TOTAL_MEMORY=16777216 -s ALLOW_MEMORY_GROWTH=1   --bind --post-js /home/walter/kalwalt-github/artoolkitX_em_2d/Source/artoolkitx.js/ARX_additions.js -s EXPORTED_FUNCTIONS='['_arwUpdateAR', '_arwCapture', '_arwGetProjectionMatrix', '_arwQueryTrackableVisibilityAndTransformation', '_arwGetTrackablePatternConfig', '_arwGetTrackablePatternImage', '_arwLoadOpticalParams']' -s EXTRA_EXPORTED_RUNTIME_METHODS='['ccall', 'cwrap', 'FS', 'setValue']' @CMakeFiles/artoolkitx.dir/objects1.rsp  -o artoolkitx.js @CMakeFiles/artoolkitx.dir/linklibs.rsp
error: Linking globals named 'jpeg_natural_order': symbol multiply defined!
shared:ERROR: Failed to run llvm optimizations: 
artoolkitx.js/CMakeFiles/artoolkitx.dir/build.make:124: recipe for target 'artoolkitx.js/artoolkitx.js' failed
make[2]: *** [artoolkitx.js/artoolkitx.js] Error 1
make[2]: uscita dalla directory "/home/walter/kalwalt-github/artoolkitX_em_2d/Source/build-em"
CMakeFiles/Makefile2:556: recipe for target 'artoolkitx.js/CMakeFiles/artoolkitx.dir/all' failed
make[1]: *** [artoolkitx.js/CMakeFiles/artoolkitx.dir/all] Error 2
make[1]: uscita dalla directory "/home/walter/kalwalt-github/artoolkitX_em_2d/Source/build-em"
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2

note in detail: error: Linking globals named 'jpeg_natural_order': symbol multiply defined!

[kalwalt]

i found the cause of the error!

[kalwalt]

i think that i can also remove the Opencv libjpeg compilation, need to be verified.

[kalwalt]

There is also a STB_IMAGE option in Emscripten since by 2013 maybe we can add also this? If yes we could add also to the 'official' version.