title: Icons for custom file types (iOS or OS X)
body: <p>I'm looking for information/documentation on creating a custom icon for a document type in my iOS app. I am sure I have seen some Apple developer guide with information about this, but I have been searching and cannot find it!</p>
  
  <p>In the app's Info.plist I have specified a custom document type, and a corresponding exported UTI (conforming to com.apple.package). Xcode makes it quite easy to specify images for these under the "Info" tab of the target settings, but I can't find the information regarding what sizes they should be, or in what situations the document icon will be visible. I believe that iOS automatically creates a 'default' document icon for you using the app icon (as per <a href="http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/MobileHIG/IconsImages/IconsImages.html#//apple_ref/doc/uid/TP40006556-CH14-SW15" rel="noreferrer">this section</a> of the HIG), so if I made it possible for users to share the document via email, another user with the app installed on their iOS device would see this default document icon.</p>
  
  <p>Where else might this document icon be seen? Currently in iTunes file sharing the document appears as a directory with the custom file extension - presumably this would change if an icon was specified for the document? When viewing one of the documents in the OS X file system, it appears as a standard white document (i.e. looks like an unknown file type) - is there any way for this to appear with the proper icon, or would the user need a Mac app installed that specifies such a file type?</p>