HTML/CSS - Automatically set height width from background image? - html

Question

Longshot... I don't think this is possible but I've been shocked before!
I anchor tags, all of which have background images, all 300px wide but their heights all vary. Is there anyway to set these without actually having to type out the height? Sort of setting it to the bg url's dimensions?
Thanks!
I don't think people understand - My fault for rushing the question.
Here's code as an example:
#ex-1 {width: 300px; height: 410px; background: url('/image-1.jpg');}
#ex-2 {width: 300px; height: 420px; background: url('/image-2.jpg');}
#ex-3 {width: 300px; height: 430px; background: url('/image-3.jpg');}
#ex-4 {width: 300px; height: 440px; background: url('/image-3.jpg');}
I'd like to NOT set the height, and it set automatically using CSS only. I don't want to use image tags.
I wasn't sure if this was possible, I assume not.
Thanks

Answer 1

A simple way of doing this is to add an image like this and then make it hidden i used visibility:hidden http://jsfiddle.net/gztpsfkw/1/
i just saw that you don't want to use <img> tags but as for here the image is being hidden and it takes up the space.
<img src="http://placekitten.com/300/301" />aa
And apply the css
a{
display:block;
background-image:url('http://placekitten.com/300/301');
width:100px;
height:auto;
}
img{
visibility:hidden;
}

Answer 2

We can use a visibility: hidden way:
<img src="http://lorempixel.com/100/200/" />
CSS
a {background: url("http://lorempixel.com/100/200/") center center no-repeat; width: 100px;}
a img {visibility: hidden;}
Fiddle: http://jsfiddle.net/praveenscience/vhjxfgtw/
JavaScript Solution
Procedure
To set the height, dynamically, you need to use JavaScript. So, you can get the computed value by adding a <img /> tag and computing the value by setting the src. The pseudo code would have been like this:
Get the computed value of background-image.
Attach it to a new <img /> element in the DOM.
Get the height of the new <img /> element.
Set the height of the fake background <div>.
JavaScript
$(document).ready(function () {
bg = $(".bg").css("background-image");
$("body").append('<img id="faux" src="' + bg.substring(4, bg.length-1) + '" />');
height = $("#faux").outerHeight();
$("#faux").remove();
$(".bg").height(height);
});
Fiddle: http://jsfiddle.net/praveenscience/rcL3xj0x/
If you don't want to use inline CSS, you can use this:
$("style").append('.bg {height: ' + height + 'px}');

Answer 3

If you're looking for a way to make the background images fill all the space available then use background-size: cover

Answer 4

I think you're looking for something like this:
function setBackgroundImage(element, src) {
var img = new Image();
img.onload = function() {
element.style.height = img.height+'px';
element.style.backgroundImage = 'url('+img.src+')';
}
img.src = src;
}
Or, if you need to scale the images for the width:
function setImage(element, src) {
var img = new Image();
img.onload = function() {
var sizeRatio = element.offsetWidth / img.width;
element.style.height = (sizeRatio * img.height)+'px';
element.style.backgroundImage = 'url('+img.src+')';
element.style.backgroundSize = 'cover';
}
img.src = src;
}

Answer 5

Side Note: The <a> tag is not a block level element. In order for the <a> to have a height and a width you need to make it a block level element to show the background image.
You would use: display: block
Now for your question... In order to get the background image, with out having to manual type it in you can use a little jQUery to make your life a lot easier. I have modified your CSS and HTML a little bit to accomodate the jQuery.
CodePen Example
#links { overflow: hidden; }
#links a { display: block; float: left; width: 300px; height: 200px;
/* generic height set in case there is no background image */ }
#ex-1 { background: url('http://www.google.com/images/srpr/logo11w.png');}
#ex-2 { background: url('http://www.bing.com/s/a/hpc12.png');}
#ex-3 { background: url('http://www.google.com/images/srpr/logo11w.png');}
#ex-4 { background: url('http://www.bing.com/s/a/hpc12.png');}
<div id="links">
</div>
Here is the jquery. It will loop through all your images and set the height according to your background image
$(document).ready(function(){
$('#links a').each(function(){
var temp = $(this).css('background-image');
temp = temp.replace('url("', '').replace('")', '');
var newImg = new Image();
newImg.src = temp;
imageHeight = newImg.height;
imageWidth = newImg.width;
$(this).css('height', imageHeight);
});
});