how to change opacity of background image in html code example

Example 1: set background image opacity

#bg{
background-image: url('images/wood1.jpg');
opacity:0.2;
width:300px;
height:300px;
}

Example 2: background image opacity css

/* Two ways to make images opaque */

div {
	background-color : rgba(120, 120, 120, 0.5) 
   	/* the 0.5 is the value of opacity on a scale of 0-1 */
}

/* OR */

div {
	background-color : blue
    opacity : 50%
}

Example 3: change transparancy img css

img {
  opacity: 0.5;
}

Example 4: css background image opacity

/*
  You have to fake it, as there is no such property
*/

div {
  width: 200px;  /* Image Width */
  height: 200px; /* Image Height */
  display: block;
  position: relative;
}

div::after {
  content: "";
  background: url(image.jpg);
  opacity: 0.5;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  position: absolute;
  z-index: -1;   
}