function image_style_deliver

Page callback: Generates a derivative, given a style and image path.

After generating an image, transfer it to the requesting agent.

Parameters

$style: The image style

$scheme: The file scheme, for example 'public' for public files.

File

modules/image/image.module, line 817

Code

function image_style_deliver($style, $scheme = NULL) {
    $args = func_get_args();
    array_shift($args);
    array_shift($args);
    $target = implode('/', $args);
    $image_uri = $scheme . '://' . $target;
    $image_uri = file_uri_normalize_dot_segments($image_uri);
    if (file_stream_wrapper_valid_scheme($scheme)) {
        $normalized_target = file_uri_target($image_uri);
        if ($normalized_target !== FALSE) {
            if (!in_array($scheme, variable_get('file_sa_core_2023_005_schemes', array()))) {
                $parts = explode('/', $normalized_target);
                if (array_intersect($parts, array(
                    '.',
                    '..',
                ))) {
                    return MENU_NOT_FOUND;
                }
            }
        }
    }
    // Check that the style is defined, the scheme is valid.
    $valid = !empty($style) && !empty($scheme) && file_stream_wrapper_valid_scheme($scheme);
    // Also validate the derivative token. Sites which require image derivatives
    // to be generated without a token can set the 'image_allow_insecure_derivatives'
    // variable to TRUE to bypass the latter check, but this will increase the
    // site's vulnerability to denial-of-service attacks. To prevent this
    // variable from leaving the site vulnerable to the most serious attacks, a
    // token is always required when a derivative of a derivative is requested.)
    $token = isset($_GET[IMAGE_DERIVATIVE_TOKEN]) ? $_GET[IMAGE_DERIVATIVE_TOKEN] : '';
    $token_is_valid = $token === image_style_path_token($style['name'], $image_uri) || $token === image_style_path_token($style['name'], $scheme . '://' . $target);
    if (!variable_get('image_allow_insecure_derivatives', FALSE) || strpos(ltrim($target, '\\/'), 'styles/') === 0) {
        $valid = $valid && $token_is_valid;
    }
    if (!$valid) {
        return MENU_ACCESS_DENIED;
    }
    $derivative_uri = image_style_path($style['name'], $image_uri);
    $derivative_scheme = file_uri_scheme($derivative_uri);
    if ($token_is_valid) {
        $is_public = $scheme !== 'private';
    }
    else {
        $core_schemes = array(
            'public',
            'private',
            'temporary',
        );
        $additional_public_schemes = array_diff(variable_get('file_additional_public_schemes', array()), $core_schemes);
        $public_schemes = array_merge(array(
            'public',
        ), $additional_public_schemes);
        $is_public = in_array($derivative_scheme, $public_schemes, TRUE);
    }
    if ($scheme == 'private' && file_exists($derivative_uri)) {
        file_download($scheme, file_uri_target($derivative_uri));
    }
    $headers = array();
    if (!$is_public) {
        $headers = file_download_headers($image_uri);
        if (empty($headers)) {
            return MENU_ACCESS_DENIED;
        }
    }
    // Confirm that the original source image exists before trying to process it.
    if (!_image_source_image_exists($image_uri, $token_is_valid)) {
        watchdog('image', 'Source image at %source_image_path not found while trying to generate derivative image at %derivative_path.', array(
            '%source_image_path' => $image_uri,
            '%derivative_path' => $derivative_uri,
        ));
        return MENU_NOT_FOUND;
    }
    // Don't start generating the image if the derivative already exists or if
    // generation is in progress in another thread.
    $lock_name = 'image_style_deliver:' . $style['name'] . ':' . drupal_hash_base64($image_uri);
    if (!file_exists($derivative_uri)) {
        $lock_acquired = lock_acquire($lock_name);
        if (!$lock_acquired) {
            // Tell client to retry again in 3 seconds. Currently no browsers are known
            // to support Retry-After.
            drupal_add_http_header('Status', '503 Service Unavailable');
            drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
            drupal_add_http_header('Retry-After', 3);
            print t('Image generation in progress. Try again shortly.');
            drupal_exit();
        }
    }
    // Try to generate the image, unless another thread just did it while we were
    // acquiring the lock.
    $success = file_exists($derivative_uri) || image_style_create_derivative($style, $image_uri, $derivative_uri);
    if (!empty($lock_acquired)) {
        lock_release($lock_name);
    }
    if ($success) {
        $image = image_load($derivative_uri);
        $headers['Content-Type'] = $image->info['mime_type'];
        $headers['Content-Length'] = $image->info['file_size'];
        file_transfer($image->source, $headers);
    }
    else {
        watchdog('image', 'Unable to generate the derived image located at %path.', array(
            '%path' => $derivative_uri,
        ));
        drupal_add_http_header('Status', '500 Internal Server Error');
        drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
        print t('Error generating image.');
        drupal_exit();
    }
}