css make image always show bottom code example

Example 1: make image darker in css

#myimage {
    filter: brightness(50%);
}

Example 2: CSS make image fill whole background

html { 
  background: url(images/bg.jpg) no-repeat 
    center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}