Crop image into square and then to circle using pure CSS?

I'm trying to make a circle out of images with different sizes and different shapes (some rectangle, some sqaure, some portrait, some landscape).

When I'm using: clip-path: circle(50% at 50% 50%); or border-radius: 50%;, it turns the image into a perfect circle, only if the image is square:

Is there a way to crop an image into a square and then use one of these methods to make it a perfect circle:

1. Using pure CSS withou using background-image (most images are given the background image from server side),
2. Keeping a 50% ratio - without losing aspect ratio - (both if border-radius or clip-path)(Images size may vary).

Here's a code snippet to show a square image and a rectangle image:

.clipped {
    clip-path: circle(50% at 50% 50%);
}

Square<br>
<img src='http://i.imgur.com/d5byNNR.jpg' width="100" class='clipped' /><br><br>
Rectangle<br>
<img src='http://i.imgur.com/22W12EQ.jpg' width="100" class='clipped' />