get_attachment_fields_to_edit

 * @param array   $form_fields An array of attachment form fields.
 * @param WP_Post $post        The WP_Post attachment object.
 * @return array Filtered attachment form fields.
 */
function media_post_single_attachment_fields_to_edit( $form_fields, $post ) {
	unset( $form_fields['image_url'] );
	return $form_fields;
}

/**
 * Filters input from media_upload_form_handler() and assigns a default
 * post_title from the file name if none supplied.
 *
 * Illustrates the use of the {@see 'attachment_fields_to_save'} filter
 * which can be used to add default values to any field before saving to DB.
 *
 * @since 2.5.0
 *
 * @param array $post       The WP_Post attachment object converted to an array.
 * @param array $attachment An array of attachment metadata.
 * @return array Filtered attachment post object.
 */
function image_attachment_fields_to_save( $post, $attachment ) {
	if ( 'image' === substr( $post['post_mime_type'], 0, 5 ) ) {
		if ( strlen( trim( $post['post_title'] ) ) == 0 ) {
			$attachment_url                           = ( isset( $post['attachment_url'] ) ) ? $post['attachment_url'] : $post['guid'];
			$post['post_title']                       = preg_replace( '/\.\w+$/', '', wp_basename( $attachment_url ) );
			$post['errors']['post_title']['errors'][] = __( 'Empty Title filled from filename.' );
		}
	}

	return $post;
}

/**
 * Retrieves the media element HTML to send to the editor.
 *
 * @since 2.5.0
 *
 * @param string  $html
 * @param integer $attachment_id
 * @param array   $attachment
 * @return string
 */
function image_media_send_to_editor( $html, $attachment_id, $attachment ) {
	$post = get_post( $attachment_id );

	if ( 'image' === substr( $post->post_mime_type, 0, 5 ) ) {
		$url   = $attachment['url'];
		$align = ! empty( $attachment['align'] ) ? $attachment['align'] : 'none';
		$size  = ! empty( $attachment['image-size'] ) ? $attachment['image-size'] : 'medium';
		$alt   = ! empty( $attachment['image_alt'] ) ? $attachment['image_alt'] : '';
		$rel   = ( strpos( $url, 'attachment_id' ) || get_attachment_link( $attachment_id ) === $url );

		return get_image_send_to_editor( $attachment_id, $attachment['post_excerpt'], $attachment['post_title'], $align, $url, $rel, $size, $alt );
	}

	return $html;
}

/**
 * Retrieves the attachment fields to edit form fields.
 *
 * @since 2.5.0
 *
 * @param WP_Post $post
 * @param array   $errors
 * @return array
 */
function get_attachment_fields_to_edit( $post, $errors = null ) {
	if ( is_int( $post ) ) {
		$post = get_post( $post );
	}

	if ( is_array( $post ) ) {
		$post = new WP_Post( (object) $post );
	}

	$image_url = wp_get_attachment_url( $post->ID );

	$edit_post = sanitize_post( $post, 'edit' );

	$form_fields = array(
		'post_title'   => array(
			'label' => __( 'Title' ),
			'value' => $edit_post->post_title,
		),
		'image_alt'    => array(),
		'post_excerpt' => array(
			'label' => __( 'Caption' ),
			'input' => 'html',
			'html'  => wp_caption_input_textarea( $edit_post ),
		),
		'post_content' => array(
			'label' => __( 'Description' ),
			'value' => $edit_post->post_content,
			'input' => 'textarea',
		),
		'url'          => array(
			'label' => __( 'Link URL' ),
			'input' => 'html',
			'html'  => image_link_input_fields( $post, get_option( 'image_default_link_type' ) ),
			'helps' => __( 'Enter a link URL or click above for presets.' ),
		),
		'menu_order'   => array(
			'label' => __( 'Order' ),
			'value' => $edit_post->menu_order,
		),
		'image_url'    => array(
			'label' => __( 'File URL' ),
			'input' => 'html',
			'html'  => "<input type='text' class='text urlfield' readonly='readonly' name='attachments[$post->ID][url]' value='" . esc_attr( $image_url ) . "' /><br />",
			'value' => wp_get_attachment_url( $post->ID ),
			'helps' => __( 'Location of the uploaded file.' ),
		),
	);