function slider_upload_dir($uploads) {
    $siteurl = get_option( 'siteurl' );
    $uploads['path'] = WP_CONTENT_DIR . '/slider';
    $uploads['url'] = $siteurl . '/wp-content/slider';
    $uploads['subdir'] = '';
    $uploads['basedir'] = $uploads['path'];
    $uploads['baseurl'] = $uploads['url'];
    $uploads['error'] = false;
    return $uploads;
}
add_filter('upload_dir', 'slider_upload_dir');