AtariInputFilter is missing cropping to 84x84 after rescaling to 110x84

[gal-leibovich]

According to the original DQN paper, observation preprocessing should be done as -

The raw frames are preprocessed by first converting their RGB representation to gray-scale and down-sampling it to a 110×84 image. The final input representation is obtained by cropping an 84 × 84 region of the image that roughly captures the playing area.

Our AtariInputFilter, on the other hand, rescales directly to 84x84, without first rescaling to 110x84, and then finally cropping to 84x84.

Chances are this issue has a fairly low impact. Yet, it might have some small impact on Atari benchmark results.