带有下载文件名的Google App Engine getImageServingUrl

Question

I'm using getImageServingUrl method to generate URL to an image and it works nicely along with options listed at List of all the App Engine images service get_serving_url() URI options

I can add "d" option to force file download instead of just presenting it in the browser. The thing is that file name defaults to "unnamed.[ext]" (where [ext] is source file extension). Is there a way I can pass the original filename somewhere to the request?

I can use CloudStorageTools::serve to save file under given name but for example I can't use the image resizing features then.

Answer 1

I am not aware of any option that would allow this. But I have a concept for another way, that is a bit complicated, but might be a good option for you. You can use nginx to build a reverse proxy, that will serve the google images for you through your own domain. Then you could send the filename in your original request as a parameter. In nginx you can get rid of the filename parameter from the request before proxying the request and add it as a header to define the filename in the response. This is pretty straighforward as a process in your nginx config:

location /image-storage/ {
    expires 30d;

    #Get rid of headers to be overwritten
    proxy_hide_header Pragma;
    proxy_hide_header Cache-Control;
    proxy_hide_header Content-Disposition;

    #Add caching headers
    add_header Pragma public;
    add_header Cache-Control "public";
    #If the parameter "filename" is sent, use it as filename
    if ($arg_filename) {
        add_header Content-Disposition 'inline; filename="$arg_filename"';
    }
    #If the parameter "dl_filename" is sent, use it as filename and init download (attachment)
    if ($arg_dl_filename) {
        add_header Content-Disposition 'attachment; filename="$arg_dl_filename"';
    }

    #Proxy the request to google
    proxy_pass       https://lh3.googleusercontent.com/;
    proxy_set_header Host lh3.googleusercontent.com;

    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

    proxy_buffering off;
}

This way a url like: https://yourdomain.com/image-storage/longgoogletokenhere?dl_filename=test.jpg would be proxied to https://lh3.googleusercontent.com/longgoogletokenhere?dl_filename=test.jpg and the response would get new headers for caching and filename.