Can CSS Combine Background Image and Opacity in a Single Property?

Can Background Images and Opacity Be Set in One Property?

CSS allows you to set background transparency and background images separately, but how do you achieve a transparent background image?

Example Scenario:

Consider an image that would be visually overwhelming as a background if used at full opacity. You want to reduce its opacity to around 0.2 for a more subtle effect.

Traditional Approach:

Using the background-image property alone won't adjust the image's transparency.

#main {
    background-image: url(/wp-content/uploads/2010/11/tandem.jpg); 
}

Solution: Pseudo-Element Hack

To create a transparent background image, utilize a pseudo-element:

#main {
    position: relative;
}
#main:after {
    content : "";
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    background-image: url(/wp-content/uploads/2010/11/tandem.jpg); 
    width: 100%;
    height: 100%;
    opacity : 0.2;
    z-index: -1;
}

Explanation:

• The :after pseudo-element creates a new element within the #main div.
• It has no content (content: ""), so it's not visually apparent.
• It is absolutely positioned at the top left of #main and covers its entire area.
• The reduced opacity of 0.2 makes the background image transparent.
• The z-index of -1 places the image behind the content in #main.

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