css position: absolute center horizontal and vertical up to device size code example

Example 1: vertically and horizontally center a fixed div

// you dont need to know the divs dimensions and it does not require any container divs
position: fixed; 
top: 50%;
left: 50%;
transform: translate(-50%, -50%);

Example 2: css center position absolute

.wrapper img {
  left: 50%;
  transform: translate(-50%,0);
  position: absolute;
  z-index: 1 
}