Customize WordPress login logo image

function.php

// Customize WordPress login logo image
function my_login_logo() { ?>
    <style type="text/css">
        #login h1 a, .login h1 a {
		background-image: url('<?php echo get_stylesheet_directory_uri();?>/screenshot.png') !important;
		width: 320px !important;
		height: 240px !important;
		background-size: 320px 240px !important;
        }
    </style>
<?php }
add_action( 'login_enqueue_scripts', 'my_login_logo' );