crude custom WP login logo

<?php
// change paths and file name to suit
add_action('login_head', 'custom_login_image');
function custom_login_image() {
	if ( file_exists( ABSPATH  . 'wp-content/themes/my-theme/_inc/images/my-new-logo.gif' ) ) {
	?>
	<style type="text/css">
		h1 a {
			background: url(<?php bloginfo('stylesheet_directory'); ?>/_inc/images/my-new-logo.gif) no-repeat 50% 0;
			width: 320px;
			height: 104px;
			text-indent: -9999px;
			overflow: hidden;
			padding-bottom: 15px;
			display: block;
		}
	</style>
	<?php
	}
} ?>