0.5px线框解决方案

.border {
width: 200px;
height: 200px;
margin: 0 auto;
position: relative;
}
.border::before {
content: " ";
position: absolute;
top: 0;
left: 0;
width: 200%;
height: 200%;
border: 1px solid red;
transform-origin: 0 0;
transform: scale(0.5);
}

image.png