scss实现retina屏1px边框

// =======================
//  用法：  
//  @include retina-border(1,1,1,1);
//  数值 代表 各 边框的宽度  上右下左
// =======================


@mixin _border-scale($dpr) {
  width: 100% * $dpr;
  height: 100% * $dpr;

  -webkit-transform: scale(1 / $dpr);
  -webkit-transform-origin: 0 0;
  transform: scale(1 / $dpr);
  transform-origin: 0 0;
}

@mixin _border-base() {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  pointer-events: none;
}

@mixin retina-border($top: 0, $right: 0, $bottom: 0, $left: 0, $cor: #000000) {
  position: relative;

  &::before {
    border-top: #{$top}px solid $cor;
    border-right: #{$right}px solid $cor;
    border-bottom: #{$bottom}px solid $cor;
    border-left: #{$left}px solid $cor;

    @include _border-base();

    @media screen and (-webkit-min-device-pixel-ratio: 1) {
      @include _border-scale(1);
    }

    @media screen and (-webkit-min-device-pixel-ratio: 1.5) {
      @include _border-scale(1.5);
    }

    @media screen and (-webkit-min-device-pixel-ratio: 2) {
      @include _border-scale(2);
    }

    @media screen and (-webkit-min-device-pixel-ratio: 3) {
      @include _border-scale(3);
    }

  }
}