HeroImagePaintChildren

hero_image_paint_children.dart

@override
void paintChildren(FlowPaintingContext flowPaintingContext) {
  final currentScrollPosition = scrollPosition.pixels;

  /// Calculate scale
  double scale = calculateTransformationValue(
    startValue: 1.1,
    endValue: 1.0,
    rangeInPx: heroImageHeight - topBarHeight,
    progressInRangeInPx: currentScrollPosition,
  );

  /// Calculate opacity
  double opacity = calculateTransformationValue(
    rangeInPx: heroImageHeight / 2,
    progressInRangeInPx: currentScrollPosition - ((heroImageHeight / 2) - topBarHeight),
    startValue: 1.0,
    endValue: 0.0,
  );

  flowPaintingContext.paintChild(
    0,
    transform: Matrix4.diagonal3Values(scale, scale, 1.0),
    opacity: opacity,
  );
}