这是一个使用 javascript 的解决方案:

Here is a solution using javascript:

var imgs = document.querySelectorAll('.pic');

for (var i = 0; i < imgs.length; i++) {
  imgs[i].onclick = toggleAnimation;
  imgs[i].style.webkitAnimationPlayState = 'running';
}

function toggleAnimation() {
  var style;
  for (var i = 0; i < imgs.length; i++) {
    style = imgs[i].style;
    if (style.webkitAnimationPlayState === 'running') {
      style.webkitAnimationPlayState = 'paused';
      document.body.className = 'paused';
    } else {
      style.webkitAnimationPlayState = 'running';
      document.body.className = '';
    }
  }
}

.pic {
  position: absolute;
  opacity: 0;
}

#pic1 {
  -webkit-animation: pic1 4s infinite linear;
}

#pic2 {
  -webkit-animation: pic2 4s infinite linear;
}

@-webkit-keyframes pic1 {
  0% {
    opacity: 0;
  }
  5% {
    opacity: 1;
  }
  45% {
    opacity: 1;
  }
  50% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}

@-webkit-keyframes pic2 {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0;
  }
  55% {
    opacity: 1;
  }
  95% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}

.paused {
  background-color: #ddd;
}

<img id="pic1" class="pic" src="http://placehold.it/200x200/ff0000/ffffff">
<img id="pic2" class="pic" src="http://placehold.it/200x200/ff00ff/ffffff">

jQuery 解决方案(更短、更易读):

jQuery solution (shorter and more readable):

var imgs = $('.pic'),
  playState = '-webkit-animation-play-state';

imgs.click(function() {
  imgs.css(playState, function(i, v) {
    return v === 'paused' ? 'running' : 'paused';
  });
  $('body').toggleClass('paused', $(this).css(playState) === 'paused');
});

.pic {
  position: absolute;
  opacity: 0;
}

#pic1 {
  -webkit-animation: pic1 4s infinite linear;
}

#pic2 {
  -webkit-animation: pic2 4s infinite linear;
}

@-webkit-keyframes pic1 {
  0% {
    opacity: 0;
  }
  5% {
    opacity: 1;
  }
  45% {
    opacity: 1;
  }
  50% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}

@-webkit-keyframes pic2 {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0;
  }
  55% {
    opacity: 1;
  }
  95% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}

.paused {
  background-color: #ddd;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<img id="pic1" class="pic" src="http://placehold.it/200x200/ff0000/ffffff">
<img id="pic2" class="pic" src="http://placehold.it/200x200/ff00ff/ffffff">