Maintaining aspect ratio with min/max height/width?

问题

I have a gallery on my site where users can upload images.

I would like the images to sit in a div that maintains its height, the images should be no larger than 500px in height. The width should be automatic to maintain aspect ratio.

HTML:

<div id="gallery">
    <img src="uploads/my-dynamic-img.jpg">
</div>

I've tried this CSS:

#gallery{
    height: 500px;

    img{
        max-height: 500px;
        max-width: 100%;
    }
}

The above works well, the gallery is always 500px high and images never exceed 500px in height. I run into problems though with smaller images, if a user uploads a really small image, I would like it 'blown up' to a minimum of 200px. I know this can be achieved by setting a min-height on the image, the problem with this is, if the image is less than 200px in height but say, 2000px wide, the image gets blown up to 200px in height, but then the aspect ratio is screwed, as the image is wider than the images parent div.

How can I have a min height but retain aspect ratio?

回答1:

The property you're looking for is object-fit. This is one of Opera's innovations, you can read more about it in their 2011 dev article on object-fit (yep, it's been around that long). A few years ago, I wouldn't have been able to recommend it to you, but caniuse shows that everyone else is starting to catch up:

Opera 10.6-12.1 (-o- prefix)
Chrome 31+
Opera 19+
Safari 7.1+
iOS 8+
Android 4.4+

http://caniuse.com/#search=object-fit

#gallery img {
    -o-object-fit: contain;
    object-fit: contain;
}

Using a value of contain will force the image to maintain its aspect ratio no matter what.

Alternately, you might want to use this instead:

#gallery img {
    -o-object-fit: cover;
    object-fit: cover;
    overflow: hidden;
}

http://sassmeister.com/gist/9b130efdae95bfa4338e

回答2:

The only way that I know of to possibly accomplish this is by setting either the width or height to auto.

#gallery{
    height: 500px;

    img{
        max-height: 500px;
        width: auto;
    }
}

回答3:

I don't know if this is possible using only CSS.

However, you may be able to accomplish the same thing with a few lines of JavaScript:

var img= document.querySelectorAll('img');
for(var i = 0 ; i < img.length ; i++) {
  img[i].onload= function() {
    var h= this.naturalHeight;
    h= Math.min(500,Math.max(200,h));
    this.style.height= h+'px';
  }
}

This sets the height of all images to be between 200px and 500px. The width will automatically be scaled.

var img= document.querySelectorAll('img');
for(var i = 0 ; i < img.length ; i++) {
  img[i].onload= function() {
    var h= this.naturalHeight;
    h= Math.min(500,Math.max(200,h));
  }
}

#gallery{
  height: 500px;
  width: 400px;
  overflow: hidden;
}

<div id="gallery">
  <img src="http://cdn.sstatic.net/stackexchange/img/logos/so/so-logo-med.png">

</div>

回答4:

I've been meaning to do something similar, actually. Here's something in jQuery if you're into that.

SCSS:

#gallery {
  height: 500px;

  img {
    max-height: 100%;
  }

  .small {
    width: 100%;
    max-width: 500px;
    height: auto;
  }

  .regular {
    width: auto;
    min-height: 200px;
  }
}

jQuery:

$( 'img' ).each( function() {

  var imageWidth = parseFloat( $( this ).css( 'width' ) );
  var imageHeight = parseFloat( $( this ).css( 'height' ) );

  if( imageHeight <= 200 && imageWidth >= 200 ) {
    $( this ).addClass( 'small' );
  }
  else {
    $( this ).addClass( 'regular' );
  }
});

CodePen

来源：https://stackoverflow.com/questions/27094771/maintaining-aspect-ratio-with-min-max-height-width

标签

html

css

Sass

aspect-ratio