Symfony2, GregWar image bundle crashes due to picture size

I am using GregWar image bundle to handle images on my website:

http://ift.tt/1DWShst

It works quite good until an error appeared and destroyed the application for several hours until I found the problem and removed the image so it's not blocking the load of the app.

The user uploaded a transparent PNG 8000x7000px big (yes the description of the image is ironic)

The application dies when trying to resize this picture and returns only white page, 503 error.

On my local machine I am able to resize it and no error occurs. The server is very powerful Centos 7 with enough resources.

Whats the best solution for this case?

1. Should I increase a memory limit or something like that? (currently 400MB)


2. Prevent uploading those kind of images?