<h2 id="usage">Usage</h2>

<p>The mediaGalleries API lets you prompt the user for permission to access
media galleries on the user's computer. The permission dialog contains common
media locations for the platform and allows the user to specify additional
locations. From those locations, only media files will be present in the file
system objects.</p>

<h2 id="manifest">Manifest</h2>

<p>The media galleries API has two axes of permission parameters:</p>

<ul>
  <li>the locations that can be accessed</li>
  <li>the type of access</li>
</ul>

<p>These two axes and the permission parameters on each axis are described
in the table below:</p>

<table>
    <tr>
      <th>Axis</th>
      <th>Parameter</th>
      <th>Effect</th>
    </tr>
    <tr>
      <td rowspan="2">Locations</td>
      <td>none</td>
      <td>
        If you do not specify a location permission parameter, your app will
        not be able to access any media galleries until the user grants
        permission to access specific media galleries at runtime using the
        media gallery permission dialog.
      </td>
    </tr>
    <tr>
      <td>"allAutoDetected"</td>
      <td>
        Grants your app access to all auto-detected media galleries on the
        user's computer. This permission causes an install-time prompt to be
        displayed indicating that the app will have access to the user's media
        files.
      </td>
    </tr>
    <tr>
      <td rowspan="3">Access&nbsp;type</td>
      <td>"read"</td>
      <td>Grants your app the right to read files in media galleries.</td>
    </tr>
    <tr>
      <td>"delete"</td>
      <td>
        Grants your app the right to delete files from media galleries.
        "read" permission is a prerequisite for "delete". Specify both "read"
        and "delete" to obtain both types of permissions to media galleries.
      </td>
    </tr>
    <tr>
      <td>"copyTo"</td>
      <td>
        Grants your app the right to copy files into media galleries.
        Only valid media files that Chrome is capable of playing or displaying
        are permitted; files that Chrome is not able to validate will result
        in a security error. "read" and "delete" permissions are prerequisites
        for "copyTo". Specify "read", "delete" and "copyTo" to obtain all three
        types of permissions to media galleries.
      </td>
    </tr>
</table>

<p>Notes:</p>
<ul>
  <li>The media gallery permission dialog can be triggered programmatically.
  The user may have alternate media locations, so even if you specify
  "allAutoDetected" permsission, it is still important to provide a mechanism
  to open the permission dialog in your app.</li>

  <li>There is no write access to media galleries due to the
  file validation requirement. However, you can write files to
  a different file system like the temporary file system, and then copy
  the files into the desired media gallery.</li>

  <li>Access type permissions do not trigger an install-time prompt
  by themselves. However, the type of access will be reflected in the
  media gallery permission dialog, as well as the install-time prompt if
  "allAutoDetected" permission is requested.</li>
</ul>

<p>Below is an example of a manifest file with mediaGalleries permissions:</p>

<pre data-filename="manifest.json">
{
  "name": "My app",
  ...
  "permissions": [
    <b>{ "mediaGalleries": ["read", "allAutoDetected"] }</b>
  ],
  ...
}
</pre>

<p>This example manifest file will trigger an install-time permission prompt,
and let the app read from all auto-detected media galleries on the
user's computer. The user may add or remove galleries using the
media gallery permission dialog, after which the app will be able
to read all the media files from galleries that the user selected.</p>

<h2 id="iTunes">iTunes</h2>

<p>If present, the user's iTunes library can be accessed as a media gallery.
In addition to the media files in the library, the "iTunes Music Library.xml"
file is also presented.</p>
<p>Regardless of where the music files are actually on the disk (and where
the xml file says they are), they are mapped into an Artist/Album/Track
hierarchy like iTunes does by default.  This mapping doesn't always work
perfectly, so there are two things to note for Apps trying to match the
xml file with files in the gallery.</p>
<p>If the filenames for tracks within an album are not unique, they will be
uniquified by adding the track id in parentheses before the extension, and
if there is a colon or a slash in the artist, album, or track name, they are
turned into underscore characters.</p>

<h2 id="Picasa">Picasa</h2>

<p>If present, the user's Picasa library can also be accessed as a media
gallery. Directories on the filesystem scanned by Picasa are presented under
folders/. Picasa Albums are presented under albums/.</p>
<p>Albums and Folders that have duplicate names and dates will be uniquified
using an incrementing integer in parenthesis before the extension.</p>
<p>Duplicate filenames within the same Album will also be uniquified using an
incrementing integer in parenthesis before the extension.</p>

<h2 id="iPhoto">iPhoto</h2>

<p>If present, the user's iPhoto library can be accessed as a media gallery.
The files are structured within a subdirectory called "Albums/". Within that
subdirectory, each album in the user's iPhoto library will appear as a
subdirectory by name, and contain file entries for the photos in that album.
</p>
<p>Duplicate album names or image filenames within albums will get a
disambiguating suffix like "(NN)" where NN is a unique number.</p>
<p>Any items appearing in multiple albums in iPhoto will appear in all those
albums in the gallery.</p>
<p>If the user has modified any images within an album, there will be an
additional subdirectory called "originals/" within the album directory.
It will contain the original image with the same filename as in the parent
album subdirectory. The file as it appears in the parrent album directory
will be the one the user has invested time cropping, rotating, or
otherwise editing.</p>
Axis	Parameter	Effect
Locations	none	If you do not specify a location permission parameter, your app will not be able to access any media galleries until the user grants permission to access specific media galleries at runtime using the media gallery permission dialog.
Locations	"allAutoDetected"	Grants your app access to all auto-detected media galleries on the user's computer. This permission causes an install-time prompt to be displayed indicating that the app will have access to the user's media files.
Access type	"read"	Grants your app the right to read files in media galleries.
	"delete"	Grants your app the right to delete files from media galleries. "read" permission is a prerequisite for "delete". Specify both "read" and "delete" to obtain both types of permissions to media galleries.
	"copyTo"	Grants your app the right to copy files into media galleries. Only valid media files that Chrome is capable of playing or displaying are permitted; files that Chrome is not able to validate will result in a security error. "read" and "delete" permissions are prerequisites for "copyTo". Specify "read", "delete" and "copyTo" to obtain all three types of permissions to media galleries.