use of tf.slice to crop images

[ariG23498]

In this PR I have tried using the tf.slice method to crop images paired with the tf.image.sample_distorted_bounding_box method.

The inspiration of this comes from the official docs of tf.image.sample_distorted_bounding_box.

[ypereirars]

The arguments tf.slice accept is the image, begin and size.
I've seen you've used bbox_begin twice. Shouldn't it be bbox_begin and bbox_size?

Ex.:
tf.slice(image, bbox_begin, bbox_size)

[ariG23498]

@ypereirars you are right!
Good catch :)