anchor.diff:  import 'controller/photo_view_controller_delegate.dart';
   import 'photo_view_hero_attributes.dart';
   import 'photo_view_typedefs.dart';
  +
  +import 'dart:math' as math;
   
   typedef PhotoViewImageTapUpCallback = Function(BuildContext context,
       TapUpDetails details, PhotoViewControllerValue controllerValue);
  
positive.code: 
      updateScaleStateFromNewScale(details.scale, newScale);
  
      updateMultiple(
        scale: newScale,
        position: clampPosition(delta * details.scale),
  
negative.code:             final matrix = Matrix4.identity()
                ..translate(value.position.dx, value.position.dy)
                ..scale(scale);
              if(widget.enableRotation) {
                matrix..rotateZ(value.rotation);
              }
  
  
  
              final Widget customChildLayout = CustomSingleChildLayout(
                delegate: _CenterWithOriginalSizeDelegate(
                  scaleBoundaries.childSize,
  