questions about $args on try_files inside location with regex - nginx

Question

(sorry for my bad english)
i have a URL like this:
http://www.domain.com/resize.php?pic=images/elements/imagename.jpg&type=300crop
that php checks if that image exists and serves, if not, creates image on disk with the size specified in the type parameter and returns it.
what I wanted is to check if the image exists on disk at that size, with nginx, so run only resize.php when necessary to create the image.
I tried this, but i think that location directive doesn't operate on query parameters ($args) using regex, then loncation does not match with sample URL :(
any help please?
I need to rewrite the parameters ($args) and use them in the try_files directive... is this possible?
location ~ "^/resize\.php\?pic=images/(elements|gallery)/(.*)\.jpg&type=([0-9]{1,3}[a-z]{0,4})$)" {
try_files /images/$1/$2.jpg /imagenes/elements/thumbs/$3_$2.jpg #phpresize;
}
location #phpresize {
try_files $uri =404;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_buffering on;
proxy_pass http://www.localhost.com:8080;
}

Answer 1

You cannot match query string in location (e.g., see here and here). The only way to process requests differently depending on the query string contents is to use if and conditional rewrites.
However, if it is OK to handle requests to /resize.php which do not have expected query parameters using the #phpresize location config, you can try something like this:
map $arg_pic $image_dir {
# A subdirectory with this name should not exist.
default invalid;
~^images/(?P<img_dir>elements|gallery)/.*\.jpg$ $img_dir;
}
map $arg_pic $image_name {
# The ".*" match here might be insecure - using something like "[-a-z0-9_]+"
# would probably be better if it matches all your image names;
# choose a regexp which is appropriate for your situation.
~^images/(elements|gallery)/(?P<img_name>.*)\.jpg$ $img_name;
}
map $arg_type $image_type {
~^(?P<img_type>[0-9]{1,3}[a-z]{0,4})$ $img_type;
}
location ~ "^/resize.php$" {
try_files /images/${image_dir}/${image_name}.jpg /imagenes/elements/thumbs/${image_type}_${image_name}.jpg #phpresize;
}
location #phpresize {
# No changes from your config here.
try_files $uri =404;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_buffering on;
proxy_pass http://www.localhost.com:8080;
}