How to keep a div contained within the viewport whilst maintaining aspect ratio

问题

There exists a square div that is an arbitrary percent wide (and the same amount high) that needs to scale with the window.

It must stay within the bounds of the viewport (ie: not clipping outside) and maintain its square shape - essentially duplicating the background-size: contain; feature of CSS.

I need to support iOS Safari v3.2, so I can't use vw/vh/vmin/vmax and would strongly prefer a CSS-only solution.

回答1:

You can set it using :after in CSS

DEMO http://jsfiddle.net/kevinPHPkevin/5tzk3/307/

.wrapper:after {
    padding-top: 100%; /*Sets ratio*/
    display: block;
    content: '';
}

Explanation:

This works by inserting no content :after and then giving the div a padding top of 100%, thus pushing the bottom of the div down. If you change it to, say, padding-top: 56.25%; it would give a 16:9 ratio. The padding does not interfere with the content of the div as it is inserted :after and only elements that are associated with :after within this element would be affected. In this case there are no elements that use :after as you'd always use a new div for this effect.

Edited

DEMO http://jsfiddle.net/kevinPHPkevin/5tzk3/309/

to stop it expanding beyond a point set a max-width and max-height

.wrapper {
    width: 50%;
    display: inline-block;
    position: relative;
    max-height:350px;
    max-width:350px;
}

回答2:

To follow up on Vector's answer in regards to cropping on the bottom:

If you have access to vw/vh you can ensure the bottom never gets cropped by setting the max-width to be 100% of the viewport height, and max-height to be 100% of the viewport-width.

e.g. max-width: 100vh; max-height: 100vw;

I know the original poster indicated they did not have access to this. Just pointing this out if you find this page like I did and DO have access.

来源：https://stackoverflow.com/questions/18296378/how-to-keep-a-div-contained-within-the-viewport-whilst-maintaining-aspect-ratio

标签

css

responsive-design

aspect-ratio