I am having problems with this as well. I initially went in and uncommented the lines for the GD lib in the php.ini file and it didn't work. Then I tried what you said to do by enabling it using Wamp and restarted it. Still it's not working for me. Do you have any other ideas or troubleshooting?
I got it working, running phpinfo I noticed it was using the wrong php.ini file. I uninstalled wamp got rid of the rogue php.ini files, reinstalled and everything is working flawlessly. Thank you!