Animate CSS clip

Question

I am trying to use CSS3 transitions to animate a CSS clip with no sucess. The image just clips without the transition.

What am I missing?

#clipped {
    position:absolute;
    width: auto;
    clip: rect(100, 100, 100, 100);
    -webkit-transition: all 0.5s ease-out;
    -moz-transition: all 0.5s ease-out;
    transition: all 0.5s ease-out;
}
#clipped:hover {
    clip: rect(50px, 200px, 200px, 0);
}

Fiddle

Answer 1

Your code works just fine. You just have to give it the correct "start" values, like so:

img {
  position: absolute;
  display: block;
  clip: rect(10px, 100px, 200px, 0);
  -webkit-transition: all 0.5s ease-out;
     -moz-transition: all 0.5s ease-out;
          transition: all 0.5s ease-out;
}

img:hover {
  clip: rect(80px, 200px, 250px, 50px);
}

<img src="http://i.stack.imgur.com/Wr86X.jpg">

Answer 2

According to this site, percentages in rect aren't supported.

If you know the size of the image, you can do this: DEMO

#clipped {
    clip: rect(0, 350px, 350px, 0);
}

Or instead of using 350px, you could use much larger numbers to accommodate larger images. You may need to play around with the numbers to get an even animation.