background color semi transparent

1.transparent {
2    background-color: rgba(255, 255, 255, 0.5);
3}
4.transparent {
5    opacity: 0.5;
6}

1h1 {background-color:rgba(255,0,0,0.3);}

1div {
2  width: 200px;
3  height: 200px;
4  display: block;
5  position: relative;
6}
7
8div::after {
9  content: "";
10  background: url(image.jpg);
11  opacity: 0.5;
12  top: 0;
13  left: 0;
14  bottom: 0;
15  right: 0;
16  position: absolute;
17  z-index: -1;   
18}