sliding_cards.dart

class SlidingCard extends StatelessWidget {
  final double offset;             //<-- How far is page from being displayed
  ...

  @override
  Widget build(BuildContext context) {
    return ...
      Image.asset(
        'assets/$assetName',
        height: MediaQuery.of(context).size.height * 0.3,
        alignment: Alignment(-offset.abs(), 0),         //<-- Set the alignment
        fit: BoxFit.none,
      ),
    ...
  }
}