CSS background-image-opacity

Question

Related to How do I give text or an image a transparent background using CSS   but slightly different   I d like to know if it s possible to change the alpha value of a background image  rather than just the colour  Obviously I can just save the image with different alpha values  but I d like to be able to adjust the alpha dynamically   So far the best I ve got is    lt div style  position  relative   gt       lt div style  position  absolute  left  0px  right  0px  top  0px  bottom  0px                        background-image  url       opacity  0 5   gt  lt  div gt       lt div style  position  relative  z-index  1   gt           lt  -- Rest of content here -- gt       lt  div gt   lt  div gt    It works  but it s bulky and ugly  and messes things up in more complicated layouts

User · Answer

You can do the faded background with CSS Generated Content

Demo at http://jsfiddle.net/gaby/WktFm/508/

Html

<div class="container">
        contents
</div>

Css

.container{
    position: relative;
    z-index:1;
    overflow:hidden; /*if you want to crop the image*/
}
.container:before{
    z-index:-1;
    position:absolute;
    left:0;
    top:0;
    content: url('path/to/image.ext');
    opacity:0.4;
}

But you cannot modify the opacity as we are not allowed to modify generated content..

You could manipulate it with classes and css events though (but not sure if it fits your needs)

for example

.container:hover:before{
    opacity:1;
}

UPDATE

You can use css transitions to animate the opacity (again through classes)

demo at http://jsfiddle.net/gaby/WktFm/507/

Adding

-webkit-transition: opacity 1s linear;
-o-transition: opacity 1s linear;
-moz-transition: opacity 1s linear;
transition: opacity 1s linear;

to the .container:before rule will make the opacity animate to 1 in one second.

Compatibility

FF 5 (maybe 4 also, but do not have it installed.)
IE 9 Fails..
Webkit based browsers fail (Chrome supports it now v26 - maybe earlier versions too, but just checked with my current build), but they are aware and working on it ( https://bugs.webkit.org/show_bug.cgi?id=23209 )

.. so only the latest FF supports it for the moment.. but a nice idea, no ? :)

User · Answer

If the background doesn t have to repeat  you can use the sprite technique  sliding-doors  where you put all the images with differing opacity into one  next to each other  and then just shift them around with background-position  Or you could declare the same partially transparent background image more than once  if your target browser supports multiple backgrounds  Firefox 3 6   Safari 1 0   Chrome 1 3   Opera 10 5   Internet Explorer 9    The opacity of those multiple images should add up  the more backgrounds you define  This process of combining transparencies is called Alpha Blending and calculated as  thanks  IainFraser   a    a1   a2 1-a1  where a ranges between 0 and 1

User · Answer

Try this   lt div style  background  linear-gradient  rgba 0  0  0  0 7   rgba 0  0  0  0 7     url  image png  background-repeat  no-repeat   background-position  center   gt   lt  div gt

User · Answer

You can t edit the image via CSS  The only solution I can think of is to edit the image and change its opacity  or make different images with all the opacities needed

User · Answer

Try this trick    use css shadow with  inset  option and make the deep 200px for example  Code   box-shadow  inset 0px 0px 277px 3px  4c3f37       Also for all browsers   -moz-box-shadow  inset 0px 0px 47px 3px  4c3f37  -webkit-box-shadow  inset 0px 0px 47px 3px  4c3f37  box-shadow  inset 0px 0px 277px 3px  4c3f37    and increase number to make fill your box     Enjoy

User · Answer

id     position  relative    opacity  0 99      id  before     content        position  absolute    width  100     height  100     z-index  -1    background  url  image png      opacity  0 3      Hack with opacity 0 99  less than 1  creates z-index context so you can not worry about global z-index values   Try to remove it and see what happens in the next demo where parent wrapper has positive z-index   If your element already has z-index  then you don t need this hack   Demo

User · Answer

Here is another approach to setup gradient and stransparency with CSS  You need to play arround with the parameters a bit though   background-image  -webkit-gradient linear  left top  left bottom  color-stop 0   rgba 0  0  0  0    color-stop 100   transparent   url  gears jpg       Chrome Safari4     background-image  -webkit-linear-gradient top  transparent  transparent  url  gears jpg       Chrome10  Safari5 1     background-image     -moz-linear-gradient top  transparent  transparent  url  gears jpg       FF3 6     background-image      -ms-linear-gradient top  transparent  transparent  url  gears jpg       IE10     background-image       -o-linear-gradient top  transparent  transparent  url  gears jpg       Opera 11 10     background-image          linear-gradient to bottom  transparent  transparent  url  gears jpg       W3C

User · Answer

You can put a second element inside the element you wish to have a transparent background on    lt div class  container  gt       lt div class  container-background  gt  lt  div gt       lt div class  content  gt           Yay  happy content       lt  div gt   lt  div gt    Then make the   container-background  positioned absolutely to cover the parent element  At this point you ll be able to adjust the opacity of it without affecting the opacity of the content inside   container     container       position  relative     container  container-background       position  absolute      top  0      right  0      bottom  0      left  0      background  url background png       opacity  0 5     container  content       position  relative      z-index  1

User · Answer

body       css code that goes in your body     body  after     background  url yourfilename jpg     content        opacity  0 6    position  fixed    top  0    bottom  0    right  0    left  0    z-index  -1       width auto    height  100         So to say its the body  after you are looking for  This way the code for your body is not changed or altered only the background where you can make changes where necessary

User · Answer

class          Fallback for web browsers that doesn t support RGBa        background  rgb 0  0  0          RGBa with 0 6 opacity        background  rgba 0  0  0  0 6       Copied from  http   robertnyman com 2010 01 11 css-background-transparency-without-affecting-child-elements-through-rgba-and-filters

[html] CSS background-image-opacity?

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