how to center an image in html without css code example

Example 1: how to center an image element inside a block in css

img { display:block;
      margin-left: auto;
      margin-right:auto;
      }

Example 2: center image html

.centered {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  -o-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
  
  font-size: 20px;
  background-color: cyan;
  border: darkgreen 5px solid;
  padding: 5px;
  z-index: 100;
}