Capture Image Only When Camera is at a Specific Distance from Object

I’m building a Flutter app where the user can take pictures of objects, but I want the capture button to be enabled only when the camera is at a specific distance from the object.

I am using the camera plugin to get the live preview, and some logic to estimate the distance of the object in front of the camera.

Here’s the simplified workflow:

1. Show live camera preview.

2. Continuously estimate distance from the camera to the object.

3. Enable the capture button only when the distance is within a target range.

4. Capture and save/crop the image when allowed.

if (_capturedImage == null && _isCameraInitialized)
              ElevatedButton(
                onPressed: _captureImage,
                child: const Text('Capture Image'),
              ),


Future<void> _captureImage() async {
  if (!_isCameraInitialized || _cameraController == null) return;

  final XFile file = await _cameraController!.takePicture();

  final croppedFile = await cropToOverlay(File(file.path), scanSquareSize, context);

  setState(() {
    _capturedImage = croppedFile;
    _uploadedImageUrl = null;
    _detections = null;
  });
}

How can I reliably measure distance to an object and enable the capture button only when the distance is within a specific range in Flutter?