opacity property
      
      double
      get
      opacity
      
    
    
    
Implementation
double get opacity {
  return _opacity;
}
      
      set
      opacity
      (double value) 
      
    
    
    
Implementation
set opacity(double value) {
  if (_opacity == value) {
    return;
  }
  _opacity = value;
  markTransformDirty();
}