how to darken an image in css code example

Example 1: darken image css

.container img {
  filter: brightness(50%);
}

Example 2: how to darken background image with css

/* Answer to: "css darken background image" */

/*
  You can use the CSS3 Linear Gradient property along with your
  background-image like the code shown below.

  Here's a link to the CSS4 Linear Gradient property:
  http://www.w3schools.com/css/css3_gradients.asp
*/

#landing-wrapper {
  display: table;
  width: 100%;
  background: linear-gradient(rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5)), url('landingpagepic.jpg');
  background-position: center top;
  height: 350px;
}