Source

File: wp-admin/includes/media.php

function get_image_send_to_editor( $id, $caption, $title, $align, $url = '', $rel = false, $size = 'medium', $alt = '' ) {

	$html = get_image_tag( $id, $alt, '', $align, $size );

	if ( $rel ) {
		if ( is_string( $rel ) ) {
			$rel = ' rel="' . esc_attr( $rel ) . '"';
		} else {
			$rel = ' rel="attachment wp-att-' . intval( $id ) . '"';
		}
	} else {
		$rel = '';
	}

	if ( $url ) {
		$html = '<a href="' . esc_attr( $url ) . '"' . $rel . '>' . $html . '</a>';
	}

	/**
	 * Filters the image HTML markup to send to the editor when inserting an image.
	 *
	 * @since 2.5.0
	 *
	 * @param string       $html    The image HTML markup to send.
	 * @param int          $id      The attachment ID.
	 * @param string       $caption The image caption.
	 * @param string       $title   The image title.
	 * @param string       $align   The image alignment.
	 * @param string       $url     The image source URL.
	 * @param string|array $size    Size of image. Image size or array of width and height values
	 *                              (in that order). Default 'medium'.
	 * @param string       $alt     The image alternative, or alt, text.
	 */
	$html = apply_filters( 'image_send_to_editor', $html, $id, $caption, $title, $align, $url, $size, $alt );

	return $html;
}