Add SVG support to a WordPress installation so images display properly in admin pages. https://core.trac.wordpress.org/ticket/26591

readme.md

Add SVG support to WordPress

See https://core.trac.wordpress.org/ticket/26591 for background on this plugin.

Usage:

• Make sure your .htaccess file is writable.
• Add the plugin file to your /wp-content/plugins/ folder and activate, or to your /wp-content/mu-plugins folder.
• Visit your Permalinks page in the Admin settings section and update your permalinks. This will refresh the .htaccess file with the SVG rules.
• Check your Admin pages to make sure SVG images are now displaying properly.

me-add-svg-support.php

<?php
/**
 * Plugin Name: Add SVG Support
 * Plugin URI: https://gist.github.com/morganestes/10066447
 * Description: Adds SVG support to the `.htaccess` file so Chrome displays images in Admin correctly.
 * Version: 0.1.0
 * Author: Morgan Estes
 * Author URI: http://www.morganestes.me
 * License: GPLv2
 */
class MorganEstes_SVG {

	/**
	 * Constructor to kick off the magic.
	 */
	public function __construct() {
		$this->init_svg();
	}

	/**
	 * Add our functions inside the right hooks.
	 */
	public function init_svg() {
		add_action( 'admin_init', array( $this, 'htaccess_writable' ) );
		add_action( 'mod_rewrite_rules', array( $this, 'add_svg_htaccess' ) );

	}

	/**
	 * Show an admin notice if .htaccess isn't writable.
	 *
	 * @link https://github.com/rub1/lbrl/blob/master/lib/utils.php#L70
	 */
	function htaccess_writable() {
		if ( ! is_writable( get_home_path() . '.htaccess' ) ) {
			if ( current_user_can( 'administrator' ) ) {
				add_action( 'admin_notices', create_function( '', "echo '<div class=\"error\"><p>" . sprintf( __( 'Please make sure your <a href="%s">.htaccess</a> file is writable ', 'roots' ), admin_url( 'options-permalink.php' ) ) . "</p></div>';" ) );
			}
		}
	}


	/**
	 * Adds the SVG ruleset to the install's `.htaccess` file.
	 *
	 * Since WordPress adds the permalinks to the .htaccess file,
	 *     I'm hooking into the core mod_rewrite_rules action to
	 *     copy my rules in at the same place.
	 *
	 * @param $rules
	 *
	 * @return string
	 */
	public function add_svg_htaccess( $rules ) {

		if ( ! defined( 'FS_METHOD' ) ) {
			define( 'FS_METHOD', 'direct' );
		}

		$svg_rules = <<<EOF
# Add SVG support to the server
AddType image/svg+xml svg
AddType image/svg+xml svgz
AddEncoding x-gzip .svgz
EOF;

		return $rules . $svg_rules;
	}
}

$morganestes_svg = new MorganEstes_SVG;