Init

lib/native_opencv.dart

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+import 'dart:ffi' as ffi;
+import 'dart:io';
+import 'package:ffi/ffi.dart';
+
+// C function signatures
+typedef _CVersionFunc = ffi.Pointer<Utf8> Function();
+typedef _CProcessImageFunc = ffi.Void Function(
+    ffi.Pointer<Utf8>, ffi.Pointer<Utf8>, ffi.Double);
+
+// Dart function signatures
+typedef _VersionFunc = ffi.Pointer<Utf8> Function();
+typedef _ProcessImageFunc = void Function(
+    ffi.Pointer<Utf8>, ffi.Pointer<Utf8>, double);
+
+// Getting a library that holds needed symbols
+ffi.DynamicLibrary _openDynamicLibrary() {
+  if (Platform.isAndroid) {
+    return ffi.DynamicLibrary.open('libnative_opencv.so');
+  } else if (Platform.isWindows) {
+    return ffi.DynamicLibrary.open("native_opencv_windows_plugin.dll");
+  }
+
+  return ffi.DynamicLibrary.process();
+}
+
+ffi.DynamicLibrary _lib = _openDynamicLibrary();
+
+// Looking for the functions
+final _VersionFunc _version =
+    _lib.lookup<ffi.NativeFunction<_CVersionFunc>>('version').asFunction();
+final _ProcessImageFunc _processImage = _lib
+    .lookup<ffi.NativeFunction<_CProcessImageFunc>>('process_image')
+    .asFunction();
+
+String opencvVersion() {
+  return _version().toDartString();
+}
+
+void processImage(ProcessImageArguments args) {
+  _processImage(args.inputPath.toNativeUtf8(), args.outputPath.toNativeUtf8(),
+      args.frameRate);
+}
+
+class ProcessImageArguments {
+  final String inputPath;
+  final String outputPath;
+  final double frameRate;
+  ProcessImageArguments(this.inputPath, this.outputPath, this.frameRate);
+}