Merge pull request #15371 from Wenzhao-Xiang:gsoc_2019

[GSoC 2019] Improve the performance of JavaScript version of OpenCV (OpenCV.js)

* [GSoC 2019]

Improve the performance of JavaScript version of OpenCV (OpenCV.js):
1. Create the base of OpenCV.js performance test:
     This perf test is based on benchmark.js(https://benchmarkjs.com). And first add `cvtColor`, `Resize`, `Threshold` into it.
2. Optimize the OpenCV.js performance by WASM threads:
     This optimization is based on Web Worker API and SharedArrayBuffer, so it can be only used in browser.
3. Optimize the OpenCV.js performance by WASM SIMD:
     Add WASM SIMD backend for OpenCV Universal Intrinsics. It's experimental as WASM SIMD is still in development.

* [GSoC2019] 

1. use short license header
2. fix documentation node issue
3. remove the unused `hasSIMD128()` api

* [GSoC2019]

1. fix emscripten define
2. use fallback function for f16

* [GSoC2019]

Fix rebase issue

doc/js_tutorials/js_setup/js_setup/js_setup.markdown

@@ -107,6 +107,90 @@ Building OpenCV.js from Source
     @note
     It requires `node` installed in your development environment.
 
+-#  [optional] To build `opencv.js` with threads optimization, append `--threads` option.
+
+    For example:
+    @code{.bash}
+    python ./platforms/js/build_js.py build_js --build_wasm --threads
+    @endcode
+
+    The default threads number is the logic core number of your device. You can use `cv.parallel_pthreads_set_threads_num(number)` to set threads number by yourself and use `cv.parallel_pthreads_get_threads_num()` to get the current threads number.
+
+    @note
+    You should build wasm version of `opencv.js` if you want to enable this optimization. And the threads optimization only works in browser, not in node.js. You need to enable the `WebAssembly threads support` feature first with your browser. For example, if you use Chrome, please enable this flag in chrome://flags.
+
+-#  [optional] To build `opencv.js` with wasm simd optimization, append `--simd` option.
+
+    For example:
+    @code{.bash}
+    python ./platforms/js/build_js.py build_js --build_wasm --simd
+    @endcode
+
+    The simd optimization is experimental as wasm simd is still in development.
+
+    @note
+    Now only emscripten LLVM upstream backend supports wasm simd, refering to https://emscripten.org/docs/porting/simd.html. So you need to setup upstream backend environment with the following command first:
+    @code{.bash}
+    ./emsdk update
+    ./emsdk install latest-upstream
+    ./emsdk activate latest-upstream
+    source ./emsdk_env.sh
+    @endcode
+
+    @note
+    You should build wasm version of `opencv.js` if you want to enable this optimization. For browser, you need to enable the `WebAssembly SIMD support` feature first. For example, if you use Chrome, please enable this flag in chrome://flags. For Node.js, you need to run script with flag `--experimental-wasm-simd`.
+
+    @note
+    The simd version of `opencv.js` built by latest LLVM upstream may not work with the stable browser or old version of Node.js. Please use the latest version of unstable browser or Node.js to get new features, like `Chrome Dev`.
+
+-#  [optional] To build wasm intrinsics tests, append `--build_wasm_intrin_test` option.
+
+    For example:
+    @code{.bash}
+    python ./platforms/js/build_js.py build_js --build_wasm --simd --build_wasm_intrin_test
+    @endcode
+
+    For wasm intrinsics tests, you can use the following function to test all the cases:
+    @code{.js}
+    cv.test_hal_intrin_all()
+    @endcode
+
+    And the failed cases will be logged in the JavaScript debug console.
+
+    If you only want to test single data type of wasm intrinsics, you can use the following functions:
+    @code{.js}
+    cv.test_hal_intrin_uint8()
+    cv.test_hal_intrin_int8()
+    cv.test_hal_intrin_uint16()
+    cv.test_hal_intrin_int16()
+    cv.test_hal_intrin_uint32()
+    cv.test_hal_intrin_int32()
+    cv.test_hal_intrin_uint64()
+    cv.test_hal_intrin_int64()
+    cv.test_hal_intrin_float32()
+    cv.test_hal_intrin_float64()
+    @endcode
+
+-#  [optional] To build performance tests, append `--build_perf` option.
+
+    For example:
+    @code{.bash}
+    python ./platforms/js/build_js.py build_js --build_perf
+    @endcode
+
+    To run performance tests, launch a local web server in \<build_dir\>/bin folder. For example, node http-server which serves on `localhost:8080`.
+
+    There are some kernels now in the performance test like `cvtColor`, `resize` and `threshold`. For example, if you want to test `threshold`, please navigate the web browser to `http://localhost:8080/perf/perf_imgproc/perf_threshold.html`. You need to input the test parameter like `(1920x1080, CV_8UC1, THRESH_BINARY)`, and then click the `Run` button to run the case. And if you don't input the parameter, it will run all the cases of this kernel.
+
+    You can also run tests using Node.js.
+
+    For example, run `threshold` with parameter `(1920x1080, CV_8UC1, THRESH_BINARY)`:
+    @code{.sh}
+    cd bin/perf
+    npm install
+    node perf_threshold.js --test_param_filter="(1920x1080, CV_8UC1, THRESH_BINARY)"
+    @endcode
+
 Building OpenCV.js with Docker
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