background image 3a url opacity

1background-image: url(IMAGE_URL); /* fallback for older browsers */
2
3background-image: linear-gradient(to bottom, rgba(0,0,0,0.6) 0%,rgba(0,0,0,0.6) 100%), url(IMAGE_URL);
4

1#bg{
2background-image: url('images/wood1.jpg');
3opacity:0.2;
4width:300px;
5height:300px;
6}
7

1/*
2  You have to fake it, as there is no such property
3*/
4
5div {
6  width: 200px;  /* Image Width */
7  height: 200px; /* Image Height */
8  display: block;
9  position: relative;
10}
11
12div::after {
13  content: "";
14  background: url(image.jpg);
15  opacity: 0.5;
16  top: 0;
17  left: 0;
18  bottom: 0;
19  right: 0;
20  position: absolute;
21  z-index: -1;   
22}