Manual:Image administration/it

Questo articolo descrive come MediaWiki gestisce e memorizza i file e fornisce alcune informazioni sulla loro configurazione.

Questo vale sia per le immagini che per qualsiasi altro tipo di file che può essere caricato. Tutti i file sono memorizzati con un articolo corrispondente nel namespace "File:". Prima di MediaWiki 1.14, si usava invece lo spazio dei nomi "Image:". "Immage:" viene mantenuto come alias per la compatibilità con il passato.



Caricamenti e utilizzo delle immagini
Vedere



Abilitare il caricamento delle immagini
Per caricare i file, devono essere soddisfatte le seguenti condizioni:


 * 1) MediaWiki deve avere i caricamenti abilitati. Impostare  a vero.
 * 2) Il tipo di file deve essere consentito. Ulteriori informazioni:.
 * 3) L'utente deve far parte di un gruppo con il diritto di "upload". Per impostazione predefinita, questa opzione viene assegnata a tutti gli utenti connessi.

I caricamenti vengono fatti utilizzando Special:Upload.

Vedere, e 



Parametri importanti per la gestione dei file
Questi sono i parametri importanti:





Miniatura immagine
La sintassi delle immagini di MediaWiki consente il ridimensionamento dinamico e il thumbnailing delle immagini (vedere per un aiuto generale sul caricamento dei file).

Image thumbnailing requires either ImageMagick or GD library – neither are part of the default MediaWiki installation.

GD
PHP comes with GD enabled by default. GD will not require any configuration or modification to be used.

It is recommended to use GD on Windows systems.

GD can be downloaded from https://libgd.github.io/. In recent PHP versions this is not required.

ImageMagick
In MediaWiki, enable ImageMagick in  by setting  to true.

ImageMagick can be downloaded from https://imagemagick.org/.

Once ImageMagick is installed, you must enable ImageMagick and point MediaWiki to the  or   program on your computer in   like this:

If you use ImageMagick, set to true in LocalSettings.php. Make sure that the command is executable by the web server process. For example, Windows users will want to change the default to "C:\ImageMagick\convert.exe" (or similar).

To re-create old thumbnail files before you used ImageMagick you can use.

If rendering fails silently, check and increase.

GraphicsMagick can also be used as an alternative to ImageMagick. You will need to set to the following. E.g.:

GIF
For thumbnailing GIF-Animations under windows, you need to install ImageMagick as described above.

SVG


MediaWiki supports SVG image rendering: if enabled, SVG images can be used like other image files — they will automatically be rendered as a PNG file and thumbnailed as needed on the fly. If you're on a shared host and no SVG renderer is pre-installed, you should probably ask your provider to install it for you.

To enable SVG support:

It depends on a large number of libraries. To automatically install all these libraries, you may want to use a package manager. The Wikimedia projects use rsvg. Its SVG parsing is more strict, causing it to reject "almost valid" SVG files that other renderers accept (e.g. ). Batik relies on Java, and is much slower than rsvg, though this may not be a huge issue unless you're constantly adding SVG files. See SVG benchmarks. Requires a lot of work to get running, if not included in your distribution. Since it will be running as user  or something similar, it will try to create   and   directories in the corresponding home directory, and will fail silently, crash or hang indefinitely if it is not able to. Inkscape is preferable to rsvg (a) on Windows (it comes as a standalone package) or (b) if you have important SVGs drawn in Inkscape that do not render correctly in rsvg. Inkscape has as complicated a dependency chain as librsvg — use only if it's in your distribution or available as a complete standalone package. The same considerations apply. Sodipod is no longer under active development. This is the default, but avoid it if possible. However, it does work. On Windows, $wgConvertPath must be set to avoid a conflict with Windows' own convert.exe. One simple alternative in this scenario is to add to LocalSettings.php the line, which also allows for spaces in the path. See ImageMagick issue. Using librsvg to render SVGs to a PNG will give much more accurate results, as well as less bandwidth consumption. Direct SVG display is not supported in MediaWiki by default, unless you install extension.
 * 1) Allow upload of SVG files in the LocalSettings.php file:   Note that MediaWiki will refuse SVG files containing JavaScript, for security reasons.
 * To avoid a false positive, add  to the  file.
 * If you are using MediaWiki 1.34 or higher, is never applied and now always . You can safely remove this in your LocalSettings.php file.
 * If you get an error saying the file is corrupt, make sure is  working properly.
 * 1) Add   to  and set the renderer you want to use.
 * Available options are ImageMagick, ImagickExt , sodipodi , inkscape , batik , rsvg , and imgserv.
 * For example:
 * 1) * librsvg is fast but not very accurate.
 * 1) * Batik is the most accurate SVG renderer available, although its anti-aliasing is sometimes suboptimal.
 * 1) * Inkscape also does an accurate job of SVGs, half the speed of rsvg, but was designed for interactive graphical use; however, it comes with inkview which is a viewer/converter program – it requires a writable home directory for the user it's run as.
 * 1) * Sodipodi is the program Inkscape was forked from.
 * 1) * Since version 6.x.x ImageMagick renders SVGs, but imperfectly.
 * 1) ** To prevent thumbnail creation errors with ImageMagick, if it's ≥ 7.0.9-25, then Inkscape must also be ≥ 1.x.x. Likewise, if ImageMagick is < 7.0.9-25, then Inkscape must also be < 1.x.x.
 * 1) * The PHP Imagick extension supports SVG rendering, however the same considerations as for the regular ImageMagick apply.
 * 1) * The GD library is not capable of converting SVG images to the PNG format, at least according to Joen Asmussen's June 2008 NoScope blog.
 * 1) * Most current web browsers except Internet Explorer (until version 9) can display SVGs directly.

Set  if SVG rendering is not needed and you wish to make your users download the svg file in order to view it.

Troubleshooting
If you see a blank square instead of SVG (Chrome) or no image at all (Firefox) and all PNG links lead to 404 error and you don't see any other error message anywhere please check variable. Setting it to false may make SVG transformation deferred always. Make sure that proc_open and symlink PHP methods are enabled (they may be disabled in php.ini for security or performance reasons).

JPEG (using GD)
Simply add the following line to LocalSettings.php, this will cause auto fall back to GD library.

For errors with JPEG thumbnails, see JPEG (using GD).

TIFF
Generating thumbnails of TIFF files requires MediaWiki 1.15.0 or newer.

Consider appropriate settings for  and
 * 1) Allow upload of TIFF files in the LocalSettings.php file:
 * 1) Add   to  and set to either jpg or png to specify which type of thumbnail you wish to have generated.
 * 1) Making thumbnails of TIFF files may require system resources beyond those needed for thumbnailing JPEG, GIF, or PNG files.

Deletion of images
Files, like wiki pages, can only be deleted by users with the " (delete)" permission ( by default). Deletion of files is done by deleting the associated description page (or by clicking the "" link in the "" table).

Deletion of individual revisions
If a file has been altered, there is a revision history of the files which is displayed on the file article page. Each revision has a "" link. If this is clicked, the revision and the file are deleted.

Information about old revisions of files are stored in the table while information on old revisions of the pages are stored in the  table.

Undeleting files
Files can be undeleted in exactly the same way as normal wiki pages. The directory in which deleted files are stored is defined by. Information about deleted images are stored in the table.

Deletion of Archived Files
Since MediaWiki version 1.11, deleted images are still stored on the server by default. If you want to delete selected archived images, you can do so using the maintenance script. If you want to delete all of them completely, you can do that with the script. If you delete archived files, you can not undelete those files anymore.

Reasons for Deleting a File
When choosing to delete a file, as described above, users will be asked to provide a reason for deletion. The available reasons can be edited on the MediaWiki:Filedelete-reason-dropdown of your wiki.

Data storage
Whenever an image is uploaded, several things are created:

This page is stored and can be edited like any other page. These are stored in the thumb directory of the image directory, in a separate directory for each main file.
 * 1) An article in the file namespace with the name of the file, e.g. File:MyPicture.png.
 * 1) The file itself is stored in a folder on the file system with whitespaces merged and replaced with.
 * 1) If necessary and thumbnailing is available, thumbnailed versions of the file will be created when necessary (such as for the usage on the file description page).

If is enabled (by default), MediaWiki creates several subdirectories in the images directory.

The directory names are from the first two characters of the md5 hash of the final filename.

Folders
All image files are stored in a folder determined by (, by default).

Description of named image subfolders:

(Due to, these files may not always be automatically deleted) If these are deleted, they are automatically regenerated when needed.
 * archive: This is the storage place for files that have been replaced by newer versions.
 * temp: used for temporary storage of files during image uploading.
 * thumb: Thumbnails (automatically generated) for the files.

Depending on the configuration, there may be additional image subfolders:

See for more details on why this might be desired and how this system works.
 * math: Folder to store your rendered TeX input, see also Extension:Math or Manual:Math.
 * x/xy: If is set to true (which is the default), images will be stored in subfolders of the images, thus making file paths look like.

Database tables

 * The file description page is stored as any page in the page, text, revision etc. tables
 * - Holds some metadata such as the size of the file and the upload date.
 * - This stores information for files that have been replaced with newer versions.
 * - holds the information on the deleted files.
 * - Records what pages use a file.

Space usage
Files need considerably more space than articles. The following calculations assume a block size of 4KB with Linux/Unix servers.

The default setting is.

Space requirements for all directories:


 * image directories: 0-f/x0-f: max. 16*16 = 256 directories = 256*4 KB = 1024 KB
 * archive directories: 0-f/x0-f: max. 16*16 = 256 directories = 256*4 KB = 1024 KB
 * thumb directories: 0-f/x0-f: max. 16*16 = 256 directories = 256*4 KB = 1024 KB
 * temp directories: 0-f/x0-f: max. 16*16 = 256 directories = 256*4 KB = 1024 KB

Therefore, the basic amount of space needed without any images uploaded is 4 MB in theory (although the directories are created only when needed).

For each file we need:


 * size of the original image file + 2 KB average overhead

For files that need to be thumbnailed:


 * size of the created thumbnail(s) + 2 KB average overhead (each)
 * directory for thumbnail (4KB) (each image has its own thumbnail directory)

Examples:


 * image 20778 Byte png (small size, no thumb): 24 KB for the image: Total 24 KB
 * image 123.000 Byte jpeg (big size, auto thumb): 124 KB for the image, 4 KB for the thumb directory, 64KB for the thumb: Total: 192 KB

File Access
Uploaded files are generally served directly by the web server, not through MediaWiki. While there may be a minimal level of security through obscurity with path encryption (e.g. /c/c4/...) if is set, the path can be calculated easily from the file name and does not provide true protection.

For limiting access to authorized users, see.

Upload form
See the documentation on configuring the upload form.

Licensing
A feature of MediaWiki allows the Special:Upload Page to streamline licensing of images. Wikipedia's Upload Page has a Licensing drop down box below image summary. To make use of this feature a sysop needs to edit Licenses in the MediaWiki namespace (example: MediaWiki:Licenses). They can do this by going to the MediaWiki:Licenses page of their wiki and clicking 'create' or 'edit'.

The page MediaWiki:Licenses expects a certain format in a wiki list.

Line 1 will produce "License text" and substitute the license 1 template in the image page and transclude license 2.

Line 2 will show a greyed out header with text "Header 1:"

Line 3 will produce "Attribution ShareAlike 2.5" and transclude template cc-by-sa-2.5 on the image page.

For detailed real world example, see Wikipedia:MediaWiki:Licenses or Commons:MediaWiki:Licenses.

Foreign Repositories
It is possible to access files stored in foreign repositories, without needing to upload them to the wiki, by setting the array. This feature offers several possibilities:


 * ForeignAPIRepo accesses files from a remote MediaWiki installation, such as Wikimedia Commons, through its API
 * ForeignDBRepo accesses files through a database, and is useful for creating wiki families
 * FSRepo accesses files from a local folder

In all cases, one would be able to embed files into a page using ordinary image syntax and specifying the name of the file in the foreign repository. Note that some of the above implementations are still experimental, and might not be suitable for production sites.