AMap BitmapDescriptor 生成，配合 image_editor image_size_getter + Asset 图片

MyAMapUtils.dart

import 'dart:math';
import 'dart:typed_data';

import 'package:amap_flutter_map/amap_flutter_map.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:image_editor/image_editor.dart';
import 'package:image_size_getter/image_size_getter.dart' as isg;
import 'package:logmap/const/resource.dart';

class MapUtils {
  static final _map = <String, BitmapDescriptor>{};

  static BitmapDescriptor getAMapBitmap(String assetKey) {
    if (!_map.containsKey(assetKey)) {
      throw Exception('$assetKey not found');
    }
    return _map[assetKey]!;
  }

  static Future<BitmapDescriptor> prepareBitmapDescriptor(
    String assetKey,
  ) async {
    if (_map.containsKey(assetKey)) {
      return _map[assetKey]!;
    }
    Uint8List iconData;
    final data = await rootBundle.load(assetKey);
    final src = data.buffer.asUint8List();
    final option = ImageEditorOption();
    option.addOption(const ScaleOption(64, 64));
    option.outputFormat = const OutputFormat.png();
    final result =
        await ImageEditor.editImage(image: src, imageEditorOption: option);

    if (result == null) {
      iconData = src;
    } else {
      iconData = result;
    }

    BitmapDescriptor prepared = BitmapDescriptor.fromBytes(iconData);

    _map[assetKey] = prepared;

    return prepared;
  }

  static final _carMarkerMap = <String, BitmapDescriptor>{};

  static void clearCache() {
    _carMarkerMap.clear();
    _map.clear();
  }

  static Future<BitmapDescriptor?> makeMarkerBitmap(String carNumber) async {
    if (_carMarkerMap.containsKey(carNumber)) {
      return _carMarkerMap[carNumber]!;
    }

    final srcBottom = await _getAssetBytes(R.ASSETS_CAR_ICON_2_PNG); // 车 icon 不透明
    // final srcBottom = await _getAssetBytes(R.ASSETS_CAR_ICON_3_PNG); // 车 icon 透明
    final srcTopBg = await _getAssetBytes(R.ASSETS_CAR_INFO_BG_PNG);

    var bottomSize = isg.ImageSizeGetter.getSize(isg.MemoryInput(srcBottom));
    final topSize = isg.ImageSizeGetter.getSize(isg.MemoryInput(srcTopBg));

    final targetWidth = max(bottomSize.width, topSize.width);
    final targetHeight = bottomSize.height + topSize.height;
    final targetSize = Size(targetWidth.toDouble(), targetHeight.toDouble());

    final bottomX = (targetWidth - bottomSize.width) / 2;

    ImageMergeOption option = ImageMergeOption(
      canvasSize: targetSize,
      format: const OutputFormat.png(),
    );
    option.addImage(
      MergeImageConfig(
        position: ImagePosition(
          Offset.zero,
          Size(
            topSize.width.toDouble(),
            topSize.height.toDouble(),
          ),
        ),
        image: ImageSource.memory(srcTopBg),
      ),
    );
    option.addImage(
      MergeImageConfig(
        position: ImagePosition(
          Offset(bottomX, topSize.height.toDouble()),
          Size(
            bottomSize.width.toDouble(),
            bottomSize.height.toDouble(),
          ),
        ),
        image: ImageSource.memory(srcBottom),
      ),
    );
    final merged = await ImageMerger.mergeToMemory(option: option);

    if (merged == null) {
      return null;
    }

    final addTextOption = ImageEditorOption();

    addTextOption.addOption(
      AddTextOption()
        ..addText(
          EditorText(
            text: carNumber,
            offset: const Offset(15, 10),
            textColor: Colors.white,
          ),
        ),
    );

    addTextOption.outputFormat = const OutputFormat.png();

    final result = await ImageEditor.editImage(
      image: merged,
      imageEditorOption: addTextOption,
    );

    if (result == null) {
      return null;
    }

    final bitmapDescription = BitmapDescriptor.fromBytes(result);
    _carMarkerMap[carNumber] = bitmapDescription;
    return bitmapDescription;
  }

  static Future<Uint8List> _getAssetBytes(String key) async {
    final byteData = await rootBundle.load(key);
    return byteData.buffer.asUint8List();
  }
}