Fatal Error on upload

I just started getting this on two WP sites yesterday when uploading:

Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 750 bytes) in /home/sustaina/public_html/wp/wp-admin/admin-functions.php on line 2153

This is line 2153:
$image = imagecreatefromjpeg( $file );

I can’t find where imagecreatefromjpeg is defined. Any ideas? It is uploading the image but it’s not creating a thumbnail and the error makes it tricky to get back to the uploaded files.