Destruct image to cleanup memory

[cmodijk]

In #633 we where encountered a lot of memory leak using the imagick extension. Imagick and Imagine fix that by using the __destruct method but because we use this in a long running process the __destruct is never getting called. This pull requests fixes that issues.

[makasim]

I dont like it, kind of hack. We can add an event dispatch there, like POST_FILTER or so and you can add a listener with custom logic in your app.

[cmodijk]

@makasim I don't like it to but it don't know if an event is going to help because in the event you don't know of the imagick object is different than the previous one. And if you __destruct the images that is still being used you get other problems and errors from that.

[makasim]

Okay, can you add a comment there (with a link to the issue) cuz it is not obvious from the code what it solves.

[makasim]

@cmodijk ping

[cmodijk]

@makasim Sorry! To what issue do you want to point the link? This pull request or the original problem?

[cmodijk]

@makasim I added a comment but I'm not so good with words in English could you please check the comments?

[mattjanssen]

Thank you! I spent hours yesterday debugging this typical-PHP memory leak. I was about to submit a PR, but I see you took care of it. 👍

I also used the __destruct() method, even though it feels gross; I could think of no better way. The comments are valuable.