Pre-processing too slow about replicating-deepmind HOT 2 OPEN

1)first we should crop the string as to remove first 33 lines and last (210-193) lines. If the string is filled with pixels line by line, this should be sth like:

cropped_pixs=pixs[160_33_2:160_193_2]

2)dividing the string into substrings of length 2:
hexs=[cropped_pixs[i_2:i_2+2] for i in range(len(cropped_pixs)/2)]

3)getting the grayscale values

map(lambda x: my_array[int(x[0],16),int(x[1],16)],hexs)

4)np.reshape to 160*160
5)thumbnail

from replicating-deepmind.

(Probably) parallelised with commit bd6fc46.

Needs profiling.

from replicating-deepmind.