Greatly improving performance of the opencv engine.
Greatly improving performance of the opencv engine.

Now it doesn't create a temporary file before serving each request,
running some tests with a 400x400 image these were the results:

Resizing to 200x200
Before:  77.93 req/s
After:  121.10 req/s (+55.39%)

Pass through
Before:  48.36 req/s
After:   93.05 req/s (+92.41%)

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