How to retrieve a file or image from a content type? I'm using services module to get data from database, among those data there is an image. 

All fields are loaded except the image, the uri seems to be wrong.

here's the postman response :

  "writer": "writer1", &lt;==== ok
  "picture": "public://couverture_harry_0.jpg",&lt;=== not ok(wrong path)
  "review": null, &lt;====== ok
  "date": "2010-02-05",&lt;===== ok 


I've configured drupal to store on sites/default/files

the picture is there but the real path is : 

drupal/sites/default/files/couverture_harry_0.jpg


(if I enter this path manually on postman it shows me the picture)
But by default the path services put is wrong.

How to "configure" services or drupal to get the good path ?

EDIT
This is my custom resource to retrieve a book (livre in french) :

function my_module_get_livre($entity_id) {
// check uid &amp;&amp; entityID

$result = db_query("SELECT `field_title_value` as titre, `field_prix_value` as prix, `field_auteur_value` as auteur, `uri` as couverture, `field_resum__value` as resumé
    , `field_date_de_parution_value` as parution, `denomination_ed` as editeur,`field_nombre_de_pages_value` as pages FROM {field_data_field_titre_en_arabe} as t_ar
    inner join {field_data_field_prix} as pr on t_ar.entity_id = pr.entity_id
    inner join {field_data_field_auteur} as aut_ar on t_ar.entity_id = aut_ar.entity_id
    left join {field_data_field_photo_de_couverture} as ph_couv on t_ar.entity_id = ph_couv.entity_id
    left join {file_managed} as file on ph_couv.field_photo_de_couverture_fid = file.fid
    left join {field_data_field_resum_} as resu on t_ar.entity_id = resu.entity_id
    left join {field_data_field_date_de_parution} as d_paru on t_ar.entity_id= d_paru.entity_id
    left join {field_data_field_edit} as edi on t_ar.entity_id = edi.entity_id
    left join {editeur} as ed on edi.field_edit_target_id = ed.uid
    left join {field_data_field_nombre_de_pages} as pages on t_ar.entity_id = pages.entity_id
    WHERE t_ar.entity_id = $entity_id ")-&gt;fetchAll();

return array('code'=&gt;'0', 'response'=&gt;$result);
   }


 function my_module_livre_retrieve ($entity_id){
      return my_module_get_livre($entity_id);
    }


I've also tested this (it works) :

$fid ='2'; &lt;=== i put it manually(but it would be set by select query
$file = file_load($fid);
$realURI = $file-&gt;uri_full = file_create_url($file-&gt;uri);
var_dump($realURI);&lt;==== returns the real url (localhost/drupal/sites/...


I want to 'alter' or just put the $realURI value to every book(livre) in his field : "photo de couverture" (which is the pitcture i want)

Thank you
Yes, this is an annoyance, no doubt.  Drupal stores the uri using a public:// streamwrapper. Thankfully, someone has written the code to resolve that into a full url that gets attached to the file object for you whenever one's loaded: https://www.drupal.org/project/full_url_file_info