The php.ini memory_limit = 128M.
The GD2 library isn’t being used for these large images, they are just files embedded in the project being showed using an HTML <img> element or CSS background-image attribute.
I’m processing the files through a php script to apply Gzip compression, perhaps this could be the issue? Shortened version of the script (note: while include_once is faster it does not work for images hence using file_get_contents):
<?php /* acquire file and path from query string parameters, check exists etc */ /* output Content-Type header with appropriate MIME type */ $sData = @file_get_contents( $sPathToImageFile ); /* output caching related headers - Expires, Last-Modified, ETag */ /* return HTTP 304 not modified with 0 content length and exit if resource same as browser cache version */ if( !ob_start( 'ob_gzhandler' )) ob_start(); echo( $sData );