CSS3 background image transition

Question

I\'m trying to make a \"fade-in fade-out\" effect using the CSS transition. But I can\'t get this to work with the background image...

The CSS:

Answer 1

Considering background-images can't be animated, I created a little SCSS mixin allowing to transition between 2 different background-images using pseudo selectors before and after. They are at different z-index layers. The one that is ahead starts with opacity 0 and becomes visible with hover.

You can use it the same approach for creating animations with linear-gradients too.

scss

@mixin bkg-img-transition( $bkg1, $bkg2, $transTime:0.5s ){  
  position: relative;  
  z-index: 100; 
  &:before, &:after {
    background-size: cover;  
    content: '';    
    display: block;
    height: 100%;
    position: absolute;
    top: 0; left: 0;    
    width: 100%;    
    transition: opacity $transTime;
  }
  &:before {    
    z-index: -101;
    background-image: url("#{$bkg1}");    
  }
  &:after {    
    z-index: -100;
    opacity: 0;
    background-image: url("#{$bkg2}");    
  }
  &:hover {
     &:after{
       opacity: 1; 
     }
  }  
}

Now you can simply use it with

@include bkg-img-transition("https://picsum.photos/300/300/?random","https://picsum.photos/g/300/300");

You can check it out here: https://jsfiddle.net/pablosgpacheco/01rmg0qL/