CSS: Create Masks in WebKit (with pulse)

gistfile1.html

<img class="cutout pulse" src="http://jedidiah.eu/code/css/masks/images/periwinkle.jpg" alt="">

gistfile2.css

/**
 * Create Masks in WebKit (with pulse)
 * http://jedidiah.eu/code/css/masks/
 */
 
.cutout{
  -webkit-mask:url(http://jedidiah.eu/code/css/masks/images/heartmask.png) no-repeat center center;
}

.cutout.pulse:hover{
  -webkit-animation-name: pulsed;
  -webkit-animation-duration: 1s;
  -webkit-animation-timing-function: ease-in-out;
  -webkit-animation-iteration-count: infinite;
  -webkit-animation-direction: alternate;
  -webkit-mask-size: auto 100%;
}

@-webkit-keyframes pulsed {
  0% { -webkit-mask-size: auto 100%; }
  100% { -webkit-mask-size: auto 90%; }
}