ImageProcess/native_vision/lib/native/doc_cropper.dart

import 'dart:ffi';

import 'package:ffi/ffi.dart';
import 'package:flutter/foundation.dart';
import 'package:native_vision/edge_detection.dart';
import 'package:native_vision/native/dynamic_lib_singleton.dart';
import 'package:path_provider/path_provider.dart';

class DocCropper {
  static final bool Function(Pointer<Utf8> imgPath, Pointer<Utf8> outPath,
          Pointer<CoordinateArray> coords) _nativeDocCrop =
      DynamicLibSingleton()
          .dl
          .lookup<
              NativeFunction<
                  Bool Function(Pointer<Utf8>, Pointer<Utf8>,
                      Pointer<CoordinateArray>)>>('native_doc_crop')
          .asFunction();

  static String? _crop(Map args) {
    final tmpDir = args["tmpDir"];
    final imgPath = args["imgPath"].toString();
    final outPath =
        "$tmpDir/cropped_${DateTime.now().millisecondsSinceEpoch}.jpg";
    final outPathPtr = outPath.toNativeUtf8();
    final imgPathPtr = imgPath.toNativeUtf8();
    final succ = _nativeDocCrop(
        imgPathPtr, outPathPtr, Pointer.fromAddress(args["coordsArrPtr"]));
    malloc.free(imgPathPtr);
    malloc.free(outPathPtr);
    return succ ? outPath : null;
  }

  static Future<String?> crop(
      String imgPath, EdgeDetectionResult result) async {
    final tmpDir = (await getTemporaryDirectory()).path;
    final coordsArrPtr = result.toNativeCoords();
    final outPath = await compute(_crop, {
      "tmpDir": tmpDir,
      "imgPath": imgPath,
      "coordsArrPtr": coordsArrPtr.address
    });
    coordsArrPtr.release();
    return outPath;
  }
}