Flutter - 如何在 custompainter 中缩放和绘制图像？

Question

我正在尝试在 custompainter 上绘制图像。我正在使用 flutter custompainter video 上的示例这是我到目前为止所拥有的。我可以在图像中绘制，但无法缩放图像。如何在手势上缩放图像并在图像中绘制？我宁愿不使用任何包。

Container(
            height: double.infinity,
            width: double.infinity,
            color: Colors.black87,
            child: FittedBox(
              child: GestureDetector(
                onScaleStart: _scaleStartGesture,
                onScaleUpdate: _scaleUpdateGesture,
                onScaleEnd: (_) => _scaleEndGesture(),
                child: SizedBox(
                    height: _image.height.toDouble(),
                    width: _image.width.toDouble(),
                    child: CustomPaint(
                      willChange: true,
                      painter: ImagePainter(
                        image: _image,
                        points: points 
                      ),
                    ),
                  ),
                ),
              ),
          ),

Answer 1

合并 LongPressDraggable或 Draggable和 GestureDetector 的 onScaleUpdate；

onScaleUpdate: (s) {
             
                    if (!(s.scale == 1 && s.rotation == 0)) {
                      controller
                        ..setImageRotate(s.rotation)
                        ..setImageScale(s.scale)
                        ..setImageOffset(s.focalPoint);
                      setState(() {
                        message = controller.selectedController.toString();
                      });
                   
                  }
                },

Controller 类；

final StreamController<ImageController> _controllerStreamController =
      StreamController<ImageController>.broadcast();
  Stream<ImageController> get controllerTypeStream =>
      _controllerStreamController.stream;

  double rotateSync;
  void setImageRotate(double rotate) {
    if (selectedController == null) {
       rotateSync = rotate;
      _controllerStreamController.sink.add(this);
    }
  }

  Offset offset;
  void setImageOffset(Offset rotate) {
    if (selectedController == null) {
      offset = rotate;
      _controllerStreamController.sink.add(this);
    }
  }
  double scaleSync;    
  void setImageScale(double scale) {
    if (selectedController == null) {
      scaleSync = scale;
      _controllerStreamController.sink.add(this);
    }
  }

    

然后在“堆栈”小部件中设置图像小部件；
堆栈 -> GestureDetector -> Draggable -> Transform.scale -> Transform.translate -> Tranform.rotate -> SizedBox(ImageWidget)