grahamharper

Thanks for your help so far Jordy. I also wouldn’t recommend anyone using my code sample above. Particularly because the value of the path property of wp_upload_dir() changes to the directory for the current month if uploads use year/month folders right?

The fundamental problem here is that in several places in the code it makes the assumption that the uploads folder is in the same folder as the WordPress core files, which won’t always be the same.

This is just an idea (I haven’t checked how it would affect the CDN feature etc.) but what if we tried something more along the lines of the code below. It uses wp_upload_dir() instead of site_url().

function wr2x_get_pathinfo_from_image_src( $image_src ) {
	$uploads_url = trailingslashit( wp_upload_dir()['baseurl'] );
	if ( strpos( $image_src, $uploads_url ) === 0 ) {
		return ltrim( substr( $image_src, strlen( $uploads_url ) ), '/');
	}
	else if ( strpos( $image_src, wp_make_link_relative( $uploads_url ) ) === 0 ) {
		return ltrim( substr( $image_src, strlen( wp_make_link_relative( $uploads_url ) ) ), '/');
	}
	else {
		$img_info = parse_url( $image_src );
		return ltrim( $img_info['path'], '/' );
	}
}

// Get WordPress upload directory
function wr2x_get_wordpress_upload_root()
{
	return wp_upload_dir()['basedir'];
}

function wr2x_from_system_to_url( $file ) {
	if ( empty( $file ) )
		return "";
	$retina_pathinfo = ltrim( str_replace( wr2x_get_wordpress_upload_root(), "", $file ), '/' );
	$url = trailingslashit( wp_upload_dir()['baseurl'] ) . $retina_pathinfo;
	$url = wr2x_cdn_this( $url );
	return $url;
}

It would be great if a fix could be rolled into the plugin so I can install plugin updates without overwriting the fix.

Got it working by using wp_upload_dir. The function now looks like:

function wr2x_picture_rewrite( $buffer ) {
	if ( !isset( $buffer ) || trim( $buffer ) === '' )
		return $buffer;
	require('inc/simple_html_dom.php');

	$nodes_count = 0;
	$nodes_replaced = 0;
	$html = str_get_html( $buffer );
	foreach( $html->find( 'img' ) as $element ) {
		$nodes_count++;
		$parent = $element->parent();
		if ( $parent->tag == "picture" ) {
			wr2x_log("Found IE fallback img tag in picture tag, will ignore.");
			continue;
		}
		else {
			$file = basename( $element->src );
			$upload_dir = wp_upload_dir();
			$filepath = trailingslashit( $upload_dir['path'] ) . $file;
			$potential_retina = wr2x_get_retina( $filepath );
			$from = substr( $element, 0 );
			if ( $potential_retina != null ) {
				$retina_pathinfo = ltrim( str_replace( WP_CONTENT_DIR, "", $potential_retina ), '/' );
				$retina_url = trailingslashit( content_url() ) . $retina_pathinfo;
				$img_url = $element->src;
				$element->srcset =  "$img_url, $retina_url 2x";
				$element->src = null;
				$to = $element;
				$buffer = str_replace( trim( $from, "</> "), trim($to, "</> "), $buffer );
				wr2x_log( "Replaced img tag '$from' by '$to'" );
				$nodes_replaced++;
			}
		}
	}

	if ( wr2x_is_debug() ) {
		wr2x_log( "$nodes_replaced img tags were replaced out of $nodes_count." );
	}

	return $buffer;
}