Add support for WebAssemly using Emscripten

LICENSE.LodePNG

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+Copyright (c) 2005-2018 Lode Vandevenne
+
+This software is provided 'as-is', without any express or implied
+warranty. In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+    1. The origin of this software must not be misrepresented; you must not
+    claim that you wrote the original software. If you use this software
+    in a product, an acknowledgment in the product documentation would be
+    appreciated but is not required.
+
+    2. Altered source versions must be plainly marked as such, and must not be
+    misrepresented as being the original software.
+
+    3. This notice may not be removed or altered from any source
+    distribution.
+

wrappers/wasm/BarcodeReader.cpp

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+/*
+* Copyright 2016 Nu-book Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*      http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+#include "GenericLuminanceSource.h"
+#include "HybridBinarizer.h"
+#include "MultiFormatReader.h"
+#include "Result.h"
+#include "DecodeHints.h"
+#include "BarcodeFormat.h"
+#include "lodepng.h"
+
+#include <string>
+#include <memory>
+#include <emscripten/bind.h>
+
+#if 0
+using Binarizer = ZXing::GlobalHistogramBinarizer;
+#else
+using Binarizer = ZXing::HybridBinarizer;
+#endif
+
+struct ReadResult
+{
+    std::string format;
+    std::wstring text;
+    std::string error;
+};
+
+ReadResult readBarcodeFromPng(int bufferPtr, int bufferLength, bool tryHarder, std::string format)
+{
+    using namespace ZXing;
+	try {
+       	DecodeHints hints;
+        hints.setShouldTryHarder(tryHarder);
+        hints.setShouldTryRotate(tryHarder);
+        auto fixedFormat = BarcodeFormatFromString(format);
+        if (fixedFormat != BarcodeFormat::FORMAT_COUNT)
+            hints.setPossibleFormats({ fixedFormat });
+        MultiFormatReader reader(hints);
+
+        std::vector<unsigned char> bitmap;
+        unsigned width, height;
+        unsigned error = lodepng::decode(bitmap, width, height, reinterpret_cast<const unsigned char*>(bufferPtr), size_t(bufferLength));
+        if (error) {
+            return { "", L"", lodepng_error_text(error) };
+        }
+
+        GenericLuminanceSource source((int)width, (int)height, bitmap.data(), width * 4, 4, 0, 1, 2);
+        Binarizer binImage(std::shared_ptr<LuminanceSource>(&source, [](void*) {}));
+
+        auto result = reader.read(binImage);
+		if (result.isValid()) {
+			return { ToString(result.format()), result.text(), "" };
+		}
+	}
+	catch (const std::exception& e) {
+		return { "", L"", e.what() };
+	}
+	catch (...) {
+
+	}
+	return {};
+}
+
+EMSCRIPTEN_BINDINGS(XZing)
+{
+    using namespace emscripten;
+
+    value_object<ReadResult>("ReadResult")
+        .field("format", &ReadResult::format)
+        .field("text", &ReadResult::text)
+        .field("error", &ReadResult::error)
+        ;
+
+    function("readBarcodeFromPng", &readBarcodeFromPng);
+}

wrappers/wasm/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.1.3)
+
+project (ZXingWasm)
+
+set (ENABLE_ENCODERS ON CACHE INTERNAL "Check to include encoders")
+set (ENABLE_DECODERS ON CACHE INTERNAL "Check to include decoders")
+
+add_definitions (-DUNICODE -D_UNICODE)
+
+if (MSVC)
+    add_definitions (-D_SCL_SECURE_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -DNOMINMAX)
+
+    set (CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} /Oi /GS-")
+    set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /Oi /GS-")
+else()
+    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra")
+    set (CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -D_DEBUG")
+    set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -D_DEBUG")
+endif()
+
+include (CheckCXXCompilerFlag)
+CHECK_CXX_COMPILER_FLAG ("-std=c++11" COMPILER_SUPPORTS_CXX11)
+
+if (COMPILER_SUPPORTS_CXX11)
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+endif()
+
+add_subdirectory (${CMAKE_CURRENT_SOURCE_DIR}/../../core ${CMAKE_BINARY_DIR}/ZXingCore)
+
+add_executable (zxing
+    BarcodeReader.cpp
+    lodepng.cpp
+)
+
+set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --bind")
+
+target_link_libraries (zxing ZXingCore)