How to set transparency in CSS?

Question

css

Let's say there is a code like this

<div class="opa">
<img src="image.png">
</div>

.opa{
opacity:0.7;
background:red;
}

Picture - white icon on a transparent background. Is it possible to somehow make the transparency not affect the image itself, but only the background ? Any crutch will do)

Answer 1

background-color: rgba(255, 0, 0, 0.7);
where 0.7 -> alpha channel (transparency)