您需要将Fit设置为BoxFit.None并减小图像比例:
Stack(
alignment: Alignment.center,
children: [
SizedBox(
height: 300,
width: 300,
child: Opacity(
opacity: .5,
child: Image.network(
'https://th.bing.com/th/id/OIP.TJDY2Ff5mVD0G8oRYvxjOwHaFC?pid=ImgDet&rs=1',
fit: BoxFit.cover,
),
)),
const Align(
alignment: Alignment.center,
child: SizedBox(
height: 200,
width: 200,
child: DecoratedBox(
decoration: BoxDecoration(
color: Colors.white,
image: DecorationImage(
image: NetworkImage('https://th.bing.com/th/id/OIP.TJDY2Ff5mVD0G8oRYvxjOwHaFC?pid=ImgDet&rs=1'),
fit: BoxFit.none,
scale: .6),
))),
)
],
),
输出: