Media Placeholders

Activate this plugin to redirect all requests for missing uploaded images on your blog to your favorite placeholder image service, such as placehold.it or placekitten.com. Note that although kittens are cute, the placehold.it service is actually more useful because the background and foreground color can remain consistant across all image sizes (e.g. full size vs thumbnail in a gallery), and so it is easier to see which images in a page are related to each other. (You can change the default placehold.it service to placekitten.com by defining MISSING_UPLOADED_IMAGE_PLACEHOLDER_BUILTIN to be placekitten_color or placekitten_grayscale, or supplying those same values via the missing_uploaded_image_placeholder_builtin filter).

This plugin is for use during development only. It is expected that this plugin will be activated on your local development environment (e.g. on Vagrant or XAMPP), or on your staging server. This plugin is especially useful when working on a team where you share around a database dump but not the uploaded images (which should always be omitted from the code repository), so if you give a database dump to another developer but don’t include the uploaded images, with this plugin enabled they will see a placeholder where the uploaded image appears. This plugin is an alternative approach to what is offered by the Uploads by Proxy plugin.

If you have applied the production database to another environment which lacks the uploaded files, but you know that all images referenced in the database do exist on production, you can define the MISSING_UPLOADED_IMAGE_REDIRECT_SERVER constant or filter missing_uploaded_image_redirect_server to short-circuit the placeholder service and redirect the image request to that server.

This plugin will not work if you are on a multisite network that uses the old system for referring to uploaded files, where the URL includes /files/ which is intercepted by a rewrite rule and passed directly to ms-files.php. See #19235. Similarly, make sure that missing uploaded files get served by the WordPress 404 handler, not Apache/Nginx. If you are using Nginx with the default Varying Vagrant Vagrants config, you’ll want to remove png|jpg|jpeg|gif from the following location rule in nginx-wp-common.conf (or remove it altogether):

# Handle all static assets by serving the file directly. Add directives 
# to send expires headers and turn off 404 error logging.
location ~* .(js|css|png|jpg|jpeg|gif|ico)$ {
    expires 24h;
    log_not_found off;
}

You can add support for your own favorite placeholder services by filtering missing_uploaded_image_placeholder.
For example, you can add this to your functions.php or drop it into a mu-plugin:

<?php
/**
 * Use Flickholdr as placeholder service
 * @param null|string $url
 * @param array $args  {attached_file, width, height, attachment_id}
 */
function my_filter_missing_uploaded_image_placeholder( $url, $args ) {
    $attachment = get_post( $args['attachment_id'] );
    $tags = join( ' ', array(
        $attachment->post_title,
        $attachment->post_excerpt,
        $attachment->post_content,
        $attachment->_wp_attachment_image_alt
    ) );
    $tags = strtolower( preg_replace( '#[^A-Za-z0-9]+#', ',', $tags ) );
    $tags = trim( $tags, ',' );
    $url = sprintf( 'http://flickholdr.com/%d/%d/%s', $args['width'], $args['height'], $tags );
    return $url;
}
add_filter( 'missing_uploaded_image_placeholder', 'my_filter_missing_uploaded_image_placeholder', 10, 2 );

Development of this plugin is done on GitHub. Pull requests welcome. Please see issues reported there before going to the plugin forum.