Comment 2 for bug 1296845

Thanks for the patch. But it needs some more work:
1.) The lensfun database needs to correctly initialized (I assume you are on Linux, where lensfun is compiled with a fixed path, where this is not needed. But on other OS lensfun needs to correctly initialized before reading.)
2.) pto_gen is using the switch --distortion. For consistency I propose to use the same here instead of --lensfun.