CSS样式实现两个图片平分三角

<div class='pageOption'>
  <a href='#' class='option' >
       <img src='http://imgsrc.hubblesite.org/hu/db/images/hs-2013-06-a-large_web.jpg'>
  </a>
  <a href='#' class='option' >
        <img src='http://imgsrc.hubblesite.org/hu/db/images/hs-2009-28-b-large_web.jpg'>
  </a>
</div>

　　

body { background: gainsboro; }
.pageOption {
  overflow: hidden;
  position: relative;
  margin: 0 auto;
  width: 40em; height: 27em;
}
.option, .option img { width: 100%; height: 100%; }
.option {
  overflow: hidden;
  position: absolute;
  /* arctan(27 / 40) = 34.01935deg
   * need to skew by 90deg - 34.01935deg = 55.98065deg
  */
  transform: skewX(-55.98deg);
}
.option:first-child {
  left: -.25em;
  transform-origin: 100% 0;
}
.option:last-child {
  right: -.25em;
  transform-origin: 0 100%;
}
.option img { opacity: .75; transition: .5s; }
.option img:hover { opacity:; }
.option img, .option:after {
  transform: skewX(55.98deg);
  transform-origin: inherit;
}
.option:after {
  position: absolute;
  margin: .5em 1.65em;
  color: white;
  font: 500 1.25em Courier;
  letter-spacing: .1em;
  text-transform: uppercase;
  content: attr(data-inf);
}
.option:first-child:after { top:; left:; }
.option:last-child:after { right:; bottom:; }

效果：鼠标移入上下两块三角图片，产生交互效果