Custom Login Logo for WordPress

functions.php

<?php

//* Login Screen: Change login logo
add_action( 'login_head', 'website-name_custom_login_logo' );
function website-name_custom_login_logo() {
  echo '<style type="text/css">
    h1 a { background-image:url('.get_stylesheet_directory_uri().'/images/login.png) !important; background-size: 150px 137px !important; height: 137px !important; width: 150px !important; margin-bottom: 30px !important; padding-bottom: 0 !important; }
    .login form { margin-top: 10px !important; }

    @media only screen and (-webkit-min-device-pixel-ratio: 1.5),
    only screen and (-moz-min-device-pixel-ratio: 1.5),
    only screen and (-o-min-device-pixel-ratio: 3/2),
    only screen and (min-device-pixel-ratio: 1.5) {
      h1 a { background-image:url('.get_stylesheet_directory_uri().'/images/login@2x.png) !important; background-size: 150px 137px !important; height: 137px !important; width: 150px !important; }
  }
    </style>';
}