Is it possible to change only the alpha of a rgba background colour on hover?

Question

I have a set of tags with differing rgba background colours but the same alpha. Is it possible to write a single css style that will change only the o

Answer 1

This is about the simplest way; put this in your css stylesheet:

a:hover { color : #c00; } 

done!

Answer 2

No, that's not possible.

If you want to use rgba, you must set each value together. There's no way to only change the alpha.

Answer 3

Why not use :hover and specify a different opacity in the hover class?

a:hover {
     opacity:0.6
}

Answer 4

You could do various things to avoid having to hard code the numbers if you want to. Some of these methods only work if you use a plain white background as they're really adding white on top rather than reducing opacity. The first one should work fine for everything provided:

• you aren't already using the psuedo-element for something; and
• you can set position to relative or absolute on the <div> tag

Option 1: ::before psuedo-element:

.before_method{
  position:relative;
}
.before_method:before{
  display:block;
  content:" ";
  position:absolute;
  z-index:-1;
  background:rgb(18, 176, 41);
  top:0;
  left:0;
  right:0;
  bottom:0;
  opacity:0.5;
}
.before_method:hover:before{
  opacity:1;
}

Option 2: white gif overlay:

.image_method{
  background-color: rgb(118, 76, 41);
  background-image: url(https://upload.wikimedia.org/wikipedia/commons/f/fc/Translucent_50_percent_white.png)
}
.image_method:hover{
  background-image:none;
}

Option 3: box-shadow method:

A variation of the gif method, but may have performance issues.

.shadow_method{
  background-color: rgb(18, 176, 41);
  box-shadow:inset 0 0 0 99999px rgba(255,255,255,0.2);
}
.shadow_method:hover{
  box-shadow:none;
}

CodePen examples: http://codepen.io/chrisboon27/pen/ACdka

Answer 5

there is an alternative,you can add a linear-gradient background image onto the original color.

a{
  background: green
}
a:hover{
  background-image:linear-gradient(hsla(0,0%,0%,.2) 100%,transparent 100%) // darker
}
a:hover{
  background-image:linear-gradient(hsla(255,100%,100%,.2) 100%,transparent 100%) // lighter
}

also, with css3 filter property,you can do that too,but it seems that it will change the text color

a:hover{
   filter: brightness(80%) //darker
}
a:hover{
   filter: brightness(120%) //lighter
}

here is a jsfiddle:https://jsfiddle.net/zhangyu911013/epwyL296/2/

Answer 6

I faced a similar problem. Here's what I did and it works fine( only alpha changes on hover and also the text is not affected) by the following steps:

1) Apply a highlighted(or any of your choice) class to whichever element you wish to change background alpha of.

2) Get the background color rgba

3) Store it in a string and manipulate it(change alpha) as you want on hover(mouseenter and mouseleave)

HTML Code:

<div class="highlighted brown">Link 1</div><br><br>
<div class="highlighted green">Link 1</div>

CSS Code:

.brown {background-color: rgba(118,76,41,.8);}
.green {background-color: rgba(51,91,11,.8);}

Javascript Code:

$(document).on({

            mouseenter: function() {

            var rgba_str = $(this).css("background-color");
            var new_rgba_str ="rgba(" + rgba_str.substring(rgba_str.lastIndexOf("(")+1,rgba_str.lastIndexOf(",")) + ", 0.5)";   

                $(this).css("background-color",new_rgba_str ); 
               },

             mouseleave: function(){

                 var rgba_str = $(this).css("background-color");

            var new_rgba_str ="rgba(" + rgba_str.substring(rgba_str.lastIndexOf("(")+1,rgba_str.lastIndexOf(",")) + ", 0.8)";               
                $(this).css("background-color",new_rgba_str ); 

               }

        },'.highlighted');

Working Fiddle:http://jsfiddle.net/HGHT6/1/