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<?php
/*
 * Single image links
 */

function ccd_default_image_link() {
	$image_set = get_option( 'image_default_link_type' );
	
	if ( $image_set !== 'file' ) { // Could be 'none'
		update_option( 'image_default_link_type', 'file' );
	}
}
add_action( 'admin_init', 'ccd_default_image_link', 10 );

?>

<?php
/*
 * Gallery image links
 */

function ccd_default_gallery_link( $settings ) {
	$settings['galleryDefaults']['link'] = 'file';
	
	return $settings;
}
add_filter( 'media_view_settings', 'ccd_default_gallery_link', 10 );

?>