WordPress Grayscale Thumbnail Generation - Makes duplicates of all uploaded images in grayscale without overwriting existing media

WordPress Grayscale Thumbnail Generation

add_filter('wp_generate_attachment_metadata','rb_bw_filter');

function rb_bw_filter($meta) {

    $path = wp_upload_dir(); // get upload directory
    $file = $path['basedir'].'/'.$meta['file']; // Get full size image

    $files[] = $file; // Set up an array of image size urls

    foreach ($meta['sizes'] as $size) {
        $files[] = $path['path'].'/'.$size['file'];
    }

    foreach ($files as $file) { // iterate through each image size

        // Convert image to grayscale credit to http://ottopress.com/2011/customizing-wordpress-images/

        list($orig_w, $orig_h, $orig_type) = @getimagesize($file);

        $image = wp_load_image($file);

        imagefilter($image, IMG_FILTER_GRAYSCALE);

        switch ($orig_type) {
            case IMAGETYPE_GIF:
                $file = str_replace(".gif", "-bw.gif", $file);
                imagegif( $image, $file );
                break;
            case IMAGETYPE_PNG:
                $file = str_replace(".png", "-bw.png", $file);
                imagepng( $image, $file );
                break;
            case IMAGETYPE_JPEG:
                $file = str_replace(".jpg", "-bw.jpg", $file);
                imagejpeg( $image, $file );
                break;
        }
    }

    return $meta;
}