How to Fix PNG Support in MediaWiki

1. In LocalSettings.php, make sure that $wgEnableUploads is set to true and that "png" is in the $wgFileExtensions array:

   $wgEnableUploads       = true;
   ...
   $wgFileExtensions = array('png', 'jpg', 'jpeg','gif');
   ...
   

2. Add these two lines to LocalSettings.php:

   $wgVerifyMimeType = false;
   $wgMimeDetectorCommand = "file -bi"; 
   

   (N.B. I think that the 2nd line probably does the trick by itself, but the first line was the first, partial solution I found, and seems to do no harm.)

3. In /path/to/your/wiki/maintenance, edit rebuildImages.php and add these two lines at the top of the file (after the block of comments, preferably):

   $wgDBadminuser = "root";
   $wgDBadminpassword = "yourmysqlrootpassword";
   

4. Run that script in php command line mode:

   php rebuildImages.php
   

   (If your system has no php command line binary, try finding and installing a "php-cli" package.)

References:

• Various forum and mailing list posts found via Google, that I failed to bookmark. Sorry folks.