functions.php

<?php

/**
 * Image Attribute Fallback
 *
 */
function be_image_attr_fallback( $attr, $attachment ) {
  if( empty( $attachment->post_parent ) )
		return $attr;
	
	$title = get_the_title( $attachment->post_parent );	

	if( empty( $attr['alt'] ) )
		$attr['alt'] = $title;
		
	if( empty( $attr['title'] ) )
		$attr['title'] = $title;
		
	return $attr;
	
}
add_filter( 'wp_get_attachment_image_attributes', 'be_image_attr_fallback', 10, 2 );