Flutter 图片透明度(光暗程度)

效果

工具类

class ItemCard extends StatelessWidget {
  final img;//图片
  final title;//图标下文字
  final icon;//是否有图标
  final double height;
  final bool flag;//true无阴影

  ItemCard(this.img,this.height,{this.title="",this.icon,this.flag=false});
  @override
  Widget build(BuildContext context) {
    return Expanded(
        flex: 1,
        child:  Container(
          height: this.height,
            child: Column(
              children: <Widget>[
                Container(
                  height: flag?null:this.height,
                  child: Stack(
                    children: <Widget>[
                      ClipRRect(
                          borderRadius: BorderRadius.circular(8),
                          child: Stack(
                            children: <Widget>[
                              Image.asset(this.img,fit: BoxFit.cover,height: this.height,width: double.infinity,),
                              BackdropFilter(
                                filter: new ImageFilter.blur(sigmaX: 0.5, sigmaY: 0.5),
                                child: new Container(
                                  color: Colors.black.withOpacity(0.3),
                                ),
                              )
                            ],
                          )
                      ),
                      Positioned(
                        left: 20,
                        top: 20,
                        child:  Icon(this.icon,color:Colors.white,size: 32,),
                      ),
                      Positioned(
                          left: 20,
                          top: 52,
                          child:  Text(this.title,style: TextStyle(
                              color:Colors.white,
                              fontSize: 12,
                              fontWeight: FontWeight.w500
                          ))
                      )
                    ],
                  ),
                )
              ],
            ),
          ),
    );
  }
}